Object Attribute Path Traverser. Safely traverse the javascript attribute tree using a text path representation. You can also check the existence of the path.
For example, I didn't like to write the following code every time... humm...
const value = {
children: {
john: {hobby: [{name: "Cycling"}, {name: "Dance"}], pet: [{type: "dog", name: "Max"}]},
tom: {hobby: [{name: "Squash"}], pet: [{type: "cat", name: "Chloe"}]}
}
};
var answer = undefined;
if (value.children) {
if (value.children.john) {
if (value.children.john.hobby) {
if (Array.isArray(value.children.john.hobby)) {
if (value.children.john.hobby.length >= 2) {
if (value.children.john.hobby[1].name) {
answer = value.children.john.hobby[1].name;
}
}
}
}
}
}
or
answer = value?.children?.john?.hobby[1]?.name;
The ugly thing above is nice if you can write it like this, right?
const {AttrPath}: any = require("attrpath");
var answer = AttrPath.traverse(value, ".children.john.hobby[1].name");
Safely traverse the object path using the given path string. Also, an array may be included in the middle of the path.
npm install atttrpath
No modules depend on it.
const {AttrPath}: any = require("attrpath");
// or
import {AttrPath} from 'attrpath';
result = AttrPath.traverse(object, path [default_value]);
params | meaning |
---|---|
object: any | Target Object. |
path: string | Traverse path. The beginning of the path is "." or "[". |
e.g. | ".cat.eye.left", ".dog['leg'][1].pad" , etc... |
default_value: any | The value to return if there is no corresponding value in the object path. default is "undefined". |
default_value: function | If you give a function, give the traverse result to the first argument of the function. |
result | meaning |
---|---|
result: any | Objects obtained as a result of traverse. |
result = AttrPath.update(object, path , value);
params | meaning |
---|---|
object: any | Target Object. |
path: string | Traverse path. The beginning of the path is "." or "[". |
e.g. | ".cat.eye.left", ".dog['leg'][1].pad" , etc... |
value: any | The value to update if the path exists. |
result | meaning |
---|---|
result: boolean | Has an update. |
result = AttrPath.is_valid(path);
params | meaning |
---|---|
path: string | Traverse path. |
result | meaning |
---|---|
result: boolean | path is grammatically correct? |
If the result is Undefined, the default value is returned.
const {AttrPath} = require('attrpath');
AttrPath.traverse({}, '.path', 1);
const {AttrPath}: any = require("attrpath");
const value = {
children: {
john: {
hobby: [{name: "Cycling"}, {name: "Dance"}],
pet: [{type: "dog", name: "Max"}]
},
tom: {
hobby: [{name: "Squash"}],
pet: [{type: "cat", name: "Chloe"}]
}
}
};
console.log(AttrPath.traverse(value, '.children.john.hobby[0].name'))
> "Max"
console.log(AttrPath.traverse(value, '.children.john.hobby[1].name'))
> undefined
const Default = (n:any) => {
console.log(n);
}
AttrPath.traverse(value, '.children.john.hobby[0].name', Default)
> "Max"
console.log(AttrPath.is_valid('.children.john.hobby[0].name'))
> true
console.log(AttrPath.is_valid('.children.john.hobby[0]..name'))
> false
class Klass {
member = "name";
Member() {
return AttrPath.traverse(this, '.member');
}
}
const klass = new Klass();
console.log(klass.Member())
> "name"
class ParentKlass {
member = "name";
}
class SubKlass extends ParentKlass {
Member() {
return AttrPath.traverse(this, '.member');
}
}
const sub_klass = new SubKlass();
console.log(sub_klass.Member())
> "name"
const value = {
children: {
john: {
hobby: [{name: "Cycling"}, {name: "Dance"}],
pet: [{type: "dog", name: "Max"}]
},
tom: {
hobby: [{name: "Squash"}],
pet: [{type: "cat", name: "Chloe"}]
}
}
};
import {AttrPath} from 'attrpath';
AttrPath.traverse(value, '.children')
AttrPath.is_valid('.children["john"].hobby[1].name')
const {AttrPath} = require('attrpath');
AttrPath.traverse(value, '.children');
AttrPath.is_valid('.children["john"].hobby[1].name')
The original value can be an array.
const {AttrPath} = require('attrpath');
AttrPath.traverse([1], '[0]');
Returns Undefined if the original value is not an object.
const {AttrPath} = require('attrpath');
AttrPath.traverse(null, '.path');
AttrPath.traverse(undefined, '.path');
AttrPath.traverse(false, '.path');
AttrPath.traverse(true, '.path');
AttrPath.traverse(NaN, '.path');
AttrPath.traverse(Infinity, '.path');
AttrPath.traverse(0, '.path');
AttrPath.traverse(-1, '.path');
AttrPath.traverse("", '.path');
AttrPath.traverse("1", '.path');
AttrPath.traverse([1], '.path');
AttrPath.traverse({}, '.path');
Note that the result object is just the argument object, so mutating the result object has the side effect of modifying the argument object. This side effect can actually be useful.
const before = [{name: "Dance"}];
AttrPath.traverse(before, '[0]').name = "Breaking";
console.log(before);
[{name: "Breaking"}]
Fixed to work correctly when the key contains ".".
const value = {
"children.john": {
hobby: [{name: "Cycling"}, {name: "Dance"}],
pet: [{type: "dog", name: "Max"}]
}
};
AttrPath.traverse(value, "['children.john']");
The results of using objects, arrays, and symbols as keys are unknown.
See demo.md for unclear cases.
"AttrPath" is under MIT license.