/
expressionRewriting.js
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/
expressionRewriting.js
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ko.expressionRewriting = (function () {
var javaScriptReservedWords = ["true", "false", "null", "undefined"];
// Matches something that can be assigned to--either an isolated identifier or something ending with a property accessor
// This is designed to be simple and avoid false negatives, but could produce false positives (e.g., a+b.c).
// This also will not properly handle nested brackets (e.g., obj1[obj2['prop']]; see #911).
var javaScriptAssignmentTarget = /^(?:[$_a-z][$\w]*|(.+)(\.\s*[$_a-z][$\w]*|\[.+\]))$/i;
function getWriteableValue(expression) {
if (ko.utils.arrayIndexOf(javaScriptReservedWords, expression) >= 0)
return false;
var match = expression.match(javaScriptAssignmentTarget);
return match === null ? false : match[1] ? ('Object(' + match[1] + ')' + match[2]) : expression;
}
// The following regular expressions will be used to split an object-literal string into tokens
// These two match strings, either with double quotes or single quotes
var stringDouble = '"(?:[^"\\\\]|\\\\.)*"',
stringSingle = "'(?:[^'\\\\]|\\\\.)*'",
// Matches a regular expression (text enclosed by slashes), but will also match sets of divisions
// as a regular expression (this is handled by the parsing loop below).
stringRegexp = '/(?:[^/\\\\]|\\\\.)*/\w*',
// These characters have special meaning to the parser and must not appear in the middle of a
// token, except as part of a string.
specials = ',"\'{}()/:[\\]',
// Match text (at least two characters) that does not contain any of the above special characters,
// although some of the special characters are allowed to start it (all but the colon and comma).
// The text can contain spaces, but leading or trailing spaces are skipped.
everyThingElse = '[^\\s:,/][^' + specials + ']*[^\\s' + specials + ']',
// Match any non-space character not matched already. This will match colons and commas, since they're
// not matched by "everyThingElse", but will also match any other single character that wasn't already
// matched (for example: in "a: 1, b: 2", each of the non-space characters will be matched by oneNotSpace).
oneNotSpace = '[^\\s]',
// Create the actual regular expression by or-ing the above strings. The order is important.
bindingToken = RegExp(stringDouble + '|' + stringSingle + '|' + stringRegexp + '|' + everyThingElse + '|' + oneNotSpace, 'g'),
// Match end of previous token to determine whether a slash is a division or regex.
divisionLookBehind = /[\])"'A-Za-z0-9_$]+$/,
keywordRegexLookBehind = {'in':1,'return':1,'typeof':1};
function parseObjectLiteral(objectLiteralString) {
// Trim leading and trailing spaces from the string
var str = ko.utils.stringTrim(objectLiteralString);
// Trim braces '{' surrounding the whole object literal
if (str.charCodeAt(0) === 123) str = str.slice(1, -1);
// Split into tokens
var result = [], toks = str.match(bindingToken), key, values = [], depth = 0;
if (toks) {
// Append a comma so that we don't need a separate code block to deal with the last item
toks.push(',');
for (var i = 0, tok; tok = toks[i]; ++i) {
var c = tok.charCodeAt(0);
// A comma signals the end of a key/value pair if depth is zero
if (c === 44) { // ","
if (depth <= 0) {
result.push((key && values.length) ? {key: key, value: values.join('')} : {'unknown': key || values.join('')});
key = depth = 0;
values = [];
continue;
}
// Simply skip the colon that separates the name and value
} else if (c === 58) { // ":"
if (!depth && !key && values.length === 1) {
key = values.pop();
continue;
}
// A set of slashes is initially matched as a regular expression, but could be division
} else if (c === 47 && i && tok.length > 1) { // "/"
// Look at the end of the previous token to determine if the slash is actually division
var match = toks[i-1].match(divisionLookBehind);
if (match && !keywordRegexLookBehind[match[0]]) {
// The slash is actually a division punctuator; re-parse the remainder of the string (not including the slash)
str = str.substr(str.indexOf(tok) + 1);
toks = str.match(bindingToken);
toks.push(',');
i = -1;
// Continue with just the slash
tok = '/';
}
// Increment depth for parentheses, braces, and brackets so that interior commas are ignored
} else if (c === 40 || c === 123 || c === 91) { // '(', '{', '['
++depth;
} else if (c === 41 || c === 125 || c === 93) { // ')', '}', ']'
--depth;
// The key will be the first token; if it's a string, trim the quotes
} else if (!key && !values.length && (c === 34 || c === 39)) { // '"', "'"
tok = tok.slice(1, -1);
}
values.push(tok);
}
}
return result;
}
// Two-way bindings include a write function that allow the handler to update the value even if it's not an observable.
var twoWayBindings = {};
function preProcessBindings(bindingsStringOrKeyValueArray, bindingOptions) {
bindingOptions = bindingOptions || {};
function processKeyValue(key, val) {
var writableVal;
function callPreprocessHook(obj) {
return (obj && obj['preprocess']) ? (val = obj['preprocess'](val, key, processKeyValue)) : true;
}
if (!bindingParams) {
if (!callPreprocessHook(ko['getBindingHandler'](key)))
return;
if (twoWayBindings[key] && (writableVal = getWriteableValue(val))) {
// For two-way bindings, provide a write method in case the value
// isn't a writable observable.
propertyAccessorResultStrings.push("'" + key + "':function(_z){" + writableVal + "=_z}");
}
}
// Values are wrapped in a function so that each value can be accessed independently
if (makeValueAccessors) {
val = 'function(){return ' + val + ' }';
}
resultStrings.push("'" + key + "':" + val);
}
var resultStrings = [],
propertyAccessorResultStrings = [],
makeValueAccessors = bindingOptions['valueAccessors'],
bindingParams = bindingOptions['bindingParams'],
keyValueArray = typeof bindingsStringOrKeyValueArray === "string" ?
parseObjectLiteral(bindingsStringOrKeyValueArray) : bindingsStringOrKeyValueArray;
ko.utils.arrayForEach(keyValueArray, function(keyValue) {
processKeyValue(keyValue.key || keyValue['unknown'], keyValue.value);
});
if (propertyAccessorResultStrings.length)
processKeyValue('_ko_property_writers', "{" + propertyAccessorResultStrings.join(",") + " }");
return resultStrings.join(",");
}
return {
bindingRewriteValidators: [],
twoWayBindings: twoWayBindings,
parseObjectLiteral: parseObjectLiteral,
preProcessBindings: preProcessBindings,
keyValueArrayContainsKey: function(keyValueArray, key) {
for (var i = 0; i < keyValueArray.length; i++)
if (keyValueArray[i]['key'] == key)
return true;
return false;
},
// Internal, private KO utility for updating model properties from within bindings
// property: If the property being updated is (or might be) an observable, pass it here
// If it turns out to be a writable observable, it will be written to directly
// allBindings: An object with a get method to retrieve bindings in the current execution context.
// This will be searched for a '_ko_property_writers' property in case you're writing to a non-observable
// key: The key identifying the property to be written. Example: for { hasFocus: myValue }, write to 'myValue' by specifying the key 'hasFocus'
// value: The value to be written
// checkIfDifferent: If true, and if the property being written is a writable observable, the value will only be written if
// it is !== existing value on that writable observable
writeValueToProperty: function(property, allBindings, key, value, checkIfDifferent) {
if (!property || !ko.isObservable(property)) {
var propWriters = allBindings.get('_ko_property_writers');
if (propWriters && propWriters[key])
propWriters[key](value);
} else if (ko.isWriteableObservable(property) && (!checkIfDifferent || property.peek() !== value)) {
property(value);
}
}
};
})();
ko.exportSymbol('expressionRewriting', ko.expressionRewriting);
ko.exportSymbol('expressionRewriting.bindingRewriteValidators', ko.expressionRewriting.bindingRewriteValidators);
ko.exportSymbol('expressionRewriting.parseObjectLiteral', ko.expressionRewriting.parseObjectLiteral);
ko.exportSymbol('expressionRewriting.preProcessBindings', ko.expressionRewriting.preProcessBindings);
// Making bindings explicitly declare themselves as "two way" isn't ideal in the long term (it would be better if
// all bindings could use an official 'property writer' API without needing to declare that they might). However,
// since this is not, and has never been, a public API (_ko_property_writers was never documented), it's acceptable
// as an internal implementation detail in the short term.
// For those developers who rely on _ko_property_writers in their custom bindings, we expose _twoWayBindings as an
// undocumented feature that makes it relatively easy to upgrade to KO 3.0. However, this is still not an official
// public API, and we reserve the right to remove it at any time if we create a real public property writers API.
ko.exportSymbol('expressionRewriting._twoWayBindings', ko.expressionRewriting.twoWayBindings);
// For backward compatibility, define the following aliases. (Previously, these function names were misleading because
// they referred to JSON specifically, even though they actually work with arbitrary JavaScript object literal expressions.)
ko.exportSymbol('jsonExpressionRewriting', ko.expressionRewriting);
ko.exportSymbol('jsonExpressionRewriting.insertPropertyAccessorsIntoJson', ko.expressionRewriting.preProcessBindings);