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ast Improved comment map Feb 22, 2016
dbg minor spacing changes for gofmt compliance Feb 25, 2015
file add source map support May 2, 2016
otto Improve error reporting Jun 12, 2014
parser add support for inline source maps May 8, 2016
registry Add Array.reduceRight (sdgoij) Jun 23, 2013
repl make autocomplete an opt-in repl feature Apr 28, 2016
terst terst Apr 26, 2014
test New parser Apr 10, 2014
token Fix string representation of GREATER_OR_EQUAL Jun 21, 2014
underscore minor spacing changes for gofmt compliance Feb 25, 2015
.gitignore New parser Apr 11, 2014
DESIGN.markdown Partially fix ReferenceError origin reporting Oct 9, 2012
LICENSE Add MIT license Dec 17, 2012
Makefile Make it clearer that inline is a Perl script Jun 24, 2016
README.markdown Fix example Jan 29, 2016
array_test.go Add tests for Array sort Apr 30, 2016
bug_test.go Merge pull request #86 from sdgoij/issue86 Dec 1, 2015
builtin.go Use -- instead of -= 1, as recommended by golint Jun 24, 2016
builtin_array.go Use -- instead of -= 1, as recommended by golint Jun 24, 2016
builtin_boolean.go Value.string(), .float64(), .bool(), etc. Jun 6, 2014
builtin_date.go Improve error reporting Jun 13, 2014
builtin_error.go make call stacks aware of native functions May 7, 2016
builtin_function.go Improve error reporting Jun 13, 2014
builtin_json.go Improve error reporting Jun 13, 2014
builtin_math.go add support for an external Math.random() provider Feb 18, 2016
builtin_number.go remove redundant RangeError prefixes Apr 4, 2016
builtin_object.go Improve error reporting Jun 13, 2014
builtin_regexp.go Value.string(), .float64(), .bool(), etc. Jun 7, 2014
builtin_string.go Improve error reporting Jun 13, 2014
builtin_test.go terst Apr 25, 2014
call_test.go fix calling go functions with goStructObject arguments May 30, 2016
clone.go ensure we clone all required runtime properties May 8, 2016
clone_test.go add test for for cloning an object with a get/set property Dec 2, 2015
cmpl.go Improve error reporting Jun 13, 2014
cmpl_evaluate.go Improve error reporting Jun 13, 2014
cmpl_evaluate_expression.go Fixed TypeError message when evaluating a.b["c"] where a.b is undefined. Oct 15, 2015
cmpl_evaluate_statement.go add tests for debugger functionality Dec 5, 2015
cmpl_parse.go Added FunctionStatement Feb 19, 2016
cmpl_test.go Improve error reporting Jun 13, 2014
console.go The zero value of Value is now defined to be undefined May 28, 2014
date_test.go go vet May 28, 2014
dbg.go Update dbg Apr 16, 2013
documentation_test.go Improve error reporting Jun 13, 2014
error.go Use -- instead of -= 1, as recommended by golint Jun 24, 2016
error_native_test.go make call stacks aware of native functions May 7, 2016
error_test.go Failing test for #202 Jun 21, 2016
evaluate.go Improve error reporting Jun 13, 2014
function_stack_test.go make call stacks aware of native functions May 7, 2016
function_test.go Improve error reporting Jun 13, 2014
global.go make call stacks aware of native functions May 7, 2016
global_test.go Improve error reporting Jun 13, 2014
inline.go The zero value of Value is now defined to be undefined May 29, 2014
inline.pl Make it clearer that inline is a Perl script Jun 24, 2016
json_test.go terst Apr 26, 2014
math_test.go terst Apr 26, 2014
native_stack_test.go make call stacks aware of native functions May 7, 2016
number_test.go Fixed tests to match the updated error messages. Apr 5, 2016
object.go Improve error reporting Jun 13, 2014
object_class.go Improve error reporting Jun 13, 2014
object_test.go terst Apr 26, 2014
otto.go implement configurable stack trace limit May 8, 2016
otto_.go Fix argument processing for call Feb 12, 2015
otto_error_test.go Improve error reporting Jun 13, 2014
otto_test.go Merge pull request #176 from deoxxa/add-autocomplete-to-repl May 2, 2016
panic_test.go terst Apr 26, 2014
parser_test.go terst Apr 26, 2014
property.go Improve error reporting Jun 13, 2014
reflect_test.go refactor native function parameter conversion May 7, 2016
regexp_test.go go vet May 29, 2014
result.go The zero value of Value is now defined to be undefined May 29, 2014
runtime.go fix calling go functions with goStructObject arguments May 30, 2016
runtime_test.go add support for an external Math.random() provider Feb 18, 2016
scope.go add simple stack depth limit mechanism Apr 4, 2016
script.go add source map support May 2, 2016
script_test.go add unit test for FunctionCall CallerLocation() Mar 1, 2015
sourcemap_test.go add support for inline source maps May 8, 2016
stash.go Add Context method to aid debugging Dec 5, 2015
string_test.go terst Apr 26, 2014
testing_test.go add source map support May 2, 2016
type_arguments.go Improve error reporting Jun 13, 2014
type_array.go Use -- instead of -= 1, as recommended by golint Jun 24, 2016
type_boolean.go Value.string(), .float64(), .bool(), etc. Jun 7, 2014
type_date.go Improve error reporting Jun 13, 2014
type_error.go make call stacks aware of native functions May 7, 2016
type_function.go make call stacks aware of native functions May 7, 2016
type_go_array.go Improve error reporting Jun 13, 2014
type_go_map.go Fix Go map iteration when looping over non-string keys Mar 1, 2015
type_go_slice.go Have goSliceGetOwnProperty check methods as well Apr 27, 2016
type_go_slice_test.go Remove executable bit from source file Jun 24, 2016
type_go_struct.go Fix toReflectValue to handle Struct, Map, Slice, etc. Jun 4, 2014
type_number.go Value.string(), .float64(), .bool(), etc. Jun 7, 2014
type_reference.go Improve error reporting Jun 13, 2014
type_regexp.go Improve error reporting Jun 13, 2014
type_string.go Value.string(), .float64(), .bool(), etc. Jun 7, 2014
underscore_arrays_test.go terst Apr 26, 2014
underscore_chaining_test.go terst Apr 26, 2014
underscore_collections_test.go terst Apr 26, 2014
underscore_functions_test.go terst Apr 26, 2014
underscore_objects_test.go go vet May 29, 2014
underscore_test.go Value.string(), .float64(), .bool(), etc. Jun 7, 2014
underscore_utility_test.go terst Apr 26, 2014
value.go Consistent use of "value Value"/"vl Value" Jun 24, 2016
value_boolean.go Value.string(), .float64(), .bool(), etc. Jun 7, 2014
value_number.go Consistent use of "value Value"/"vl Value" Jun 24, 2016
value_primitive.go The zero value of Value is now defined to be undefined May 29, 2014
value_string.go Value.string(), .float64(), .bool(), etc. Jun 7, 2014
value_test.go fixes #165 - crash exporting an array with undefined as the first ele… Apr 4, 2016

README.markdown

otto

import "github.com/robertkrimen/otto"

Package otto is a JavaScript parser and interpreter written natively in Go.

http://godoc.org/github.com/robertkrimen/otto

import (
    "github.com/robertkrimen/otto"
)

Run something in the VM

vm := otto.New()
vm.Run(`
    abc = 2 + 2;
    console.log("The value of abc is " + abc); // 4
`)

Get a value out of the VM

if value, err := vm.Get("abc"); err == nil {
    if value_int, err := value.ToInteger(); err == nil {
        fmt.Printf("", value_int, err)
    }
}

Set a number

vm.Set("def", 11)
vm.Run(`
    console.log("The value of def is " + def);
    // The value of def is 11
`)

Set a string

vm.Set("xyzzy", "Nothing happens.")
vm.Run(`
    console.log(xyzzy.length); // 16
`)

Get the value of an expression

value, _ = vm.Run("xyzzy.length")
{
    // value is an int64 with a value of 16
    value, _ := value.ToInteger()
}

An error happens

value, err = vm.Run("abcdefghijlmnopqrstuvwxyz.length")
if err != nil {
    // err = ReferenceError: abcdefghijlmnopqrstuvwxyz is not defined
    // If there is an error, then value.IsUndefined() is true
    ...
}

Set a Go function

vm.Set("sayHello", func(call otto.FunctionCall) otto.Value {
    fmt.Printf("Hello, %s.\n", call.Argument(0).String())
    return otto.Value{}
})

Set a Go function that returns something useful

vm.Set("twoPlus", func(call otto.FunctionCall) otto.Value {
    right, _ := call.Argument(0).ToInteger()
    result, _ := vm.ToValue(2 + right)
    return result
})

Use the functions in JavaScript

result, _ = vm.Run(`
    sayHello("Xyzzy");      // Hello, Xyzzy.
    sayHello();             // Hello, undefined

    result = twoPlus(2.0); // 4
`)

Parser

A separate parser is available in the parser package if you're just interested in building an AST.

http://godoc.org/github.com/robertkrimen/otto/parser

Parse and return an AST

filename := "" // A filename is optional
src := `
    // Sample xyzzy example
    (function(){
        if (3.14159 > 0) {
            console.log("Hello, World.");
            return;
        }

        var xyzzy = NaN;
        console.log("Nothing happens.");
        return xyzzy;
    })();
`

// Parse some JavaScript, yielding a *ast.Program and/or an ErrorList
program, err := parser.ParseFile(nil, filename, src, 0)

otto

You can run (Go) JavaScript from the commandline with: http://github.com/robertkrimen/otto/tree/master/otto

$ go get -v github.com/robertkrimen/otto/otto

Run JavaScript by entering some source on stdin or by giving otto a filename:

$ otto example.js

underscore

Optionally include the JavaScript utility-belt library, underscore, with this import:

import (
    "github.com/robertkrimen/otto"
    _ "github.com/robertkrimen/otto/underscore"
)

// Now every otto runtime will come loaded with underscore

For more information: http://github.com/robertkrimen/otto/tree/master/underscore

Caveat Emptor

The following are some limitations with otto:

* "use strict" will parse, but does nothing.
* The regular expression engine (re2/regexp) is not fully compatible with the ECMA5 specification.

Regular Expression Incompatibility

Go translates JavaScript-style regular expressions into something that is "regexp" compatible via parser.TransformRegExp. Unfortunately, RegExp requires backtracking for some patterns, and backtracking is not supported by the standard Go engine: https://code.google.com/p/re2/wiki/Syntax

Therefore, the following syntax is incompatible:

(?=)  // Lookahead (positive), currently a parsing error
(?!)  // Lookahead (backhead), currently a parsing error
\1    // Backreference (\1, \2, \3, ...), currently a parsing error

A brief discussion of these limitations: "Regexp (?!re)" https://groups.google.com/forum/?fromgroups=#%21topic/golang-nuts/7qgSDWPIh_E

More information about re2: https://code.google.com/p/re2/

In addition to the above, re2 (Go) has a different definition for \s: [\t\n\f\r ]. The JavaScript definition, on the other hand, also includes \v, Unicode "Separator, Space", etc.

Halting Problem

If you want to stop long running executions (like third-party code), you can use the interrupt channel to do this:

package main

import (
    "errors"
    "fmt"
    "os"
    "time"

    "github.com/robertkrimen/otto"
)

var halt = errors.New("Stahp")

func main() {
    runUnsafe(`var abc = [];`)
    runUnsafe(`
    while (true) {
        // Loop forever
    }`)
}

func runUnsafe(unsafe string) {
    start := time.Now()
    defer func() {
        duration := time.Since(start)
        if caught := recover(); caught != nil {
            if caught == halt {
                fmt.Fprintf(os.Stderr, "Some code took to long! Stopping after: %v\n", duration)
                return
            }
            panic(caught) // Something else happened, repanic!
        }
        fmt.Fprintf(os.Stderr, "Ran code successfully: %v\n", duration)
    }()

    vm := otto.New()
    vm.Interrupt = make(chan func(), 1) // The buffer prevents blocking

    go func() {
        time.Sleep(2 * time.Second) // Stop after two seconds
        vm.Interrupt <- func() {
            panic(halt)
        }
    }()

    vm.Run(unsafe) // Here be dragons (risky code)
}

Where is setTimeout/setInterval?

These timing functions are not actually part of the ECMA-262 specification. Typically, they belong to the window object (in the browser). It would not be difficult to provide something like these via Go, but you probably want to wrap otto in an event loop in that case.

For an example of how this could be done in Go with otto, see natto:

http://github.com/robertkrimen/natto

Here is some more discussion of the issue:

Usage

var ErrVersion = errors.New("version mismatch")

type Error

type Error struct {
}

An Error represents a runtime error, e.g. a TypeError, a ReferenceError, etc.

func (Error) Error

func (err Error) Error() string

Error returns a description of the error

TypeError: 'def' is not a function

func (Error) String

func (err Error) String() string

String returns a description of the error and a trace of where the error occurred.

TypeError: 'def' is not a function
    at xyz (<anonymous>:3:9)
    at <anonymous>:7:1/

type FunctionCall

type FunctionCall struct {
    This         Value
    ArgumentList []Value
    Otto         *Otto
}

FunctionCall is an encapsulation of a JavaScript function call.

func (FunctionCall) Argument

func (self FunctionCall) Argument(index int) Value

Argument will return the value of the argument at the given index.

If no such argument exists, undefined is returned.

type Object

type Object struct {
}

Object is the representation of a JavaScript object.

func (Object) Call

func (self Object) Call(name string, argumentList ...interface{}) (Value, error)

Call a method on the object.

It is essentially equivalent to:

var method, _ := object.Get(name)
method.Call(object, argumentList...)

An undefined value and an error will result if:

1. There is an error during conversion of the argument list
2. The property is not actually a function
3. An (uncaught) exception is thrown

func (Object) Class

func (self Object) Class() string

Class will return the class string of the object.

The return value will (generally) be one of:

Object
Function
Array
String
Number
Boolean
Date
RegExp

func (Object) Get

func (self Object) Get(name string) (Value, error)

Get the value of the property with the given name.

func (Object) Keys

func (self Object) Keys() []string

Get the keys for the object

Equivalent to calling Object.keys on the object

func (Object) Set

func (self Object) Set(name string, value interface{}) error

Set the property of the given name to the given value.

An error will result if the setting the property triggers an exception (i.e. read-only), or there is an error during conversion of the given value.

func (Object) Value

func (self Object) Value() Value

Value will return self as a value.

type Otto

type Otto struct {
    // Interrupt is a channel for interrupting the runtime. You can use this to halt a long running execution, for example.
    // See "Halting Problem" for more information.
    Interrupt chan func()
}

Otto is the representation of the JavaScript runtime. Each instance of Otto has a self-contained namespace.

func New

func New() *Otto

New will allocate a new JavaScript runtime

func Run

func Run(src interface{}) (*Otto, Value, error)

Run will allocate a new JavaScript runtime, run the given source on the allocated runtime, and return the runtime, resulting value, and error (if any).

src may be a string, a byte slice, a bytes.Buffer, or an io.Reader, but it MUST always be in UTF-8.

src may also be a Script.

src may also be a Program, but if the AST has been modified, then runtime behavior is undefined.

func (Otto) Call

func (self Otto) Call(source string, this interface{}, argumentList ...interface{}) (Value, error)

Call the given JavaScript with a given this and arguments.

If this is nil, then some special handling takes place to determine the proper this value, falling back to a "standard" invocation if necessary (where this is undefined).

If source begins with "new " (A lowercase new followed by a space), then Call will invoke the function constructor rather than performing a function call. In this case, the this argument has no effect.

// value is a String object
value, _ := vm.Call("Object", nil, "Hello, World.")

// Likewise...
value, _ := vm.Call("new Object", nil, "Hello, World.")

// This will perform a concat on the given array and return the result
// value is [ 1, 2, 3, undefined, 4, 5, 6, 7, "abc" ]
value, _ := vm.Call(`[ 1, 2, 3, undefined, 4 ].concat`, nil, 5, 6, 7, "abc")

func (*Otto) Compile

func (self *Otto) Compile(filename string, src interface{}) (*Script, error)

Compile will parse the given source and return a Script value or nil and an error if there was a problem during compilation.

script, err := vm.Compile("", `var abc; if (!abc) abc = 0; abc += 2; abc;`)
vm.Run(script)

func (*Otto) Copy

func (in *Otto) Copy() *Otto

Copy will create a copy/clone of the runtime.

Copy is useful for saving some time when creating many similar runtimes.

This method works by walking the original runtime and cloning each object, scope, stash, etc. into a new runtime.

Be on the lookout for memory leaks or inadvertent sharing of resources.

func (Otto) Get

func (self Otto) Get(name string) (Value, error)

Get the value of the top-level binding of the given name.

If there is an error (like the binding does not exist), then the value will be undefined.

func (Otto) Object

func (self Otto) Object(source string) (*Object, error)

Object will run the given source and return the result as an object.

For example, accessing an existing object:

object, _ := vm.Object(`Number`)

Or, creating a new object:

object, _ := vm.Object(`({ xyzzy: "Nothing happens." })`)

Or, creating and assigning an object:

object, _ := vm.Object(`xyzzy = {}`)
object.Set("volume", 11)

If there is an error (like the source does not result in an object), then nil and an error is returned.

func (Otto) Run

func (self Otto) Run(src interface{}) (Value, error)

Run will run the given source (parsing it first if necessary), returning the resulting value and error (if any)

src may be a string, a byte slice, a bytes.Buffer, or an io.Reader, but it MUST always be in UTF-8.

If the runtime is unable to parse source, then this function will return undefined and the parse error (nothing will be evaluated in this case).

src may also be a Script.

src may also be a Program, but if the AST has been modified, then runtime behavior is undefined.

func (Otto) Set

func (self Otto) Set(name string, value interface{}) error

Set the top-level binding of the given name to the given value.

Set will automatically apply ToValue to the given value in order to convert it to a JavaScript value (type Value).

If there is an error (like the binding is read-only, or the ToValue conversion fails), then an error is returned.

If the top-level binding does not exist, it will be created.

func (Otto) ToValue

func (self Otto) ToValue(value interface{}) (Value, error)

ToValue will convert an interface{} value to a value digestible by otto/JavaScript.

type Script

type Script struct {
}

Script is a handle for some (reusable) JavaScript. Passing a Script value to a run method will evaluate the JavaScript.

func (*Script) String

func (self *Script) String() string

type Value

type Value struct {
}

Value is the representation of a JavaScript value.

func FalseValue

func FalseValue() Value

FalseValue will return a value representing false.

It is equivalent to:

ToValue(false)

func NaNValue

func NaNValue() Value

NaNValue will return a value representing NaN.

It is equivalent to:

ToValue(math.NaN())

func NullValue

func NullValue() Value

NullValue will return a Value representing null.

func ToValue

func ToValue(value interface{}) (Value, error)

ToValue will convert an interface{} value to a value digestible by otto/JavaScript

This function will not work for advanced types (struct, map, slice/array, etc.) and you should use Otto.ToValue instead.

func TrueValue

func TrueValue() Value

TrueValue will return a value representing true.

It is equivalent to:

ToValue(true)

func UndefinedValue

func UndefinedValue() Value

UndefinedValue will return a Value representing undefined.

func (Value) Call

func (value Value) Call(this Value, argumentList ...interface{}) (Value, error)

Call the value as a function with the given this value and argument list and return the result of invocation. It is essentially equivalent to:

value.apply(thisValue, argumentList)

An undefined value and an error will result if:

1. There is an error during conversion of the argument list
2. The value is not actually a function
3. An (uncaught) exception is thrown

func (Value) Class

func (value Value) Class() string

Class will return the class string of the value or the empty string if value is not an object.

The return value will (generally) be one of:

Object
Function
Array
String
Number
Boolean
Date
RegExp

func (Value) Export

func (self Value) Export() (interface{}, error)

Export will attempt to convert the value to a Go representation and return it via an interface{} kind.

Export returns an error, but it will always be nil. It is present for backwards compatibility.

If a reasonable conversion is not possible, then the original value is returned.

undefined   -> nil (FIXME?: Should be Value{})
null        -> nil
boolean     -> bool
number      -> A number type (int, float32, uint64, ...)
string      -> string
Array       -> []interface{}
Object      -> map[string]interface{}

func (Value) IsBoolean

func (value Value) IsBoolean() bool

IsBoolean will return true if value is a boolean (primitive).

func (Value) IsDefined

func (value Value) IsDefined() bool

IsDefined will return false if the value is undefined, and true otherwise.

func (Value) IsFunction

func (value Value) IsFunction() bool

IsFunction will return true if value is a function.

func (Value) IsNaN

func (value Value) IsNaN() bool

IsNaN will return true if value is NaN (or would convert to NaN).

func (Value) IsNull

func (value Value) IsNull() bool

IsNull will return true if the value is null, and false otherwise.

func (Value) IsNumber

func (value Value) IsNumber() bool

IsNumber will return true if value is a number (primitive).

func (Value) IsObject

func (value Value) IsObject() bool

IsObject will return true if value is an object.

func (Value) IsPrimitive

func (value Value) IsPrimitive() bool

IsPrimitive will return true if value is a primitive (any kind of primitive).

func (Value) IsString

func (value Value) IsString() bool

IsString will return true if value is a string (primitive).

func (Value) IsUndefined

func (value Value) IsUndefined() bool

IsUndefined will return true if the value is undefined, and false otherwise.

func (Value) Object

func (value Value) Object() *Object

Object will return the object of the value, or nil if value is not an object.

This method will not do any implicit conversion. For example, calling this method on a string primitive value will not return a String object.

func (Value) String

func (value Value) String() string

String will return the value as a string.

This method will make return the empty string if there is an error.

func (Value) ToBoolean

func (value Value) ToBoolean() (bool, error)

ToBoolean will convert the value to a boolean (bool).

ToValue(0).ToBoolean() => false
ToValue("").ToBoolean() => false
ToValue(true).ToBoolean() => true
ToValue(1).ToBoolean() => true
ToValue("Nothing happens").ToBoolean() => true

If there is an error during the conversion process (like an uncaught exception), then the result will be false and an error.

func (Value) ToFloat

func (value Value) ToFloat() (float64, error)

ToFloat will convert the value to a number (float64).

ToValue(0).ToFloat() => 0.
ToValue(1.1).ToFloat() => 1.1
ToValue("11").ToFloat() => 11.

If there is an error during the conversion process (like an uncaught exception), then the result will be 0 and an error.

func (Value) ToInteger

func (value Value) ToInteger() (int64, error)

ToInteger will convert the value to a number (int64).

ToValue(0).ToInteger() => 0
ToValue(1.1).ToInteger() => 1
ToValue("11").ToInteger() => 11

If there is an error during the conversion process (like an uncaught exception), then the result will be 0 and an error.

func (Value) ToString

func (value Value) ToString() (string, error)

ToString will convert the value to a string (string).

ToValue(0).ToString() => "0"
ToValue(false).ToString() => "false"
ToValue(1.1).ToString() => "1.1"
ToValue("11").ToString() => "11"
ToValue('Nothing happens.').ToString() => "Nothing happens."

If there is an error during the conversion process (like an uncaught exception), then the result will be the empty string ("") and an error.

godocdown http://github.com/robertkrimen/godocdown

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