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JavaScript 的json源码,限时发布

2024-09-06 00:09:23 前端知识 前端哥 209 128 我要收藏

Number.prototype.toJSON = this_value;

String.prototype.toJSON = this_value;

}

var gap;

var indent;

var meta;

var rep;

function quote(string) {

// If the string contains no control characters, no quote characters, and no

// backslash characters, then we can safely slap some quotes around it.

// Otherwise we must also replace the offending characters with safe escape

// sequences.

rx_escapable.lastIndex = 0;

return rx_escapable.test(string)

? “”" + string.replace(rx_escapable, function (a) {

var c = meta[a];

return typeof c === “string”

? c
“\u” + (“0000” + a.charCodeAt(0).toString(16)).slice(-4);
}) + “”"
“”" + string + “”";

}

function str(key, holder) {

// Produce a string from holder[key].

var i; // The loop counter.

var k; // The member key.

var v; // The member value.

var length;

var mind = gap;

var partial;

var value = holder[key];

// If the value has a toJSON method, call it to obtain a replacement value.

if (value && typeof value === “object” &&

typeof value.toJSON === “function”) {

value = value.toJSON(key);

}

// If we were called with a replacer function, then call the replacer to

// obtain a replacement value.

if (typeof rep === “function”) {

value = rep.call(holder, key, value);

}

// What happens next depends on the value’s type.

switch (typeof value) {

case “string”:

return quote(value);

case “number”:

// JSON numbers must be finite. Encode non-finite numbers as null.

return isFinite(value)

? String(value)
“null”;

case “boolean”:

case “null”:

// If the value is a boolean or null, convert it to a string. Note:

// typeof null does not produce “null”. The case is included here in

// the remote chance that this gets fixed someday.

return String(value);

// If the type is “object”, we might be dealing with an object or an array or

// null.

case “object”:

// Due to a specification blunder in ECMAScript, typeof null is “object”,

// so watch out for that case.

if (!value) {

return “null”;

}

// Make an array to hold the partial results of stringifying this object value.

gap += indent;

partial = [];

// Is the value an array?

if (Object.prototype.toString.apply(value) === “[object Array]”) {

// The value is an array. Stringify every element. Use null as a placeholder

// for non-JSON values.

length = value.length;

for (i = 0; i < length; i += 1) {

partial[i] = str(i, value) || “null”;

}

// Join all of the elements together, separated with commas, and wrap them in

// brackets.

v = partial.length === 0

? “[]”
gap
? “[\n” + gap + partial.join(“,\n” + gap) + “\n” + mind + “]”
“[” + partial.join(“,”) + “]”;

gap = mind;

return v;

}

// If the replacer is an array, use it to select the members to be stringified.

if (rep && typeof rep === “object”) {

length = rep.length;

for (i = 0; i < length; i += 1) {

if (typeof rep[i] === “string”) {

k = rep[i];

v = str(k, value);

if (v) {

partial.push(quote(k) + (

gap

? ": "
“:”

) + v);

}

}

}

} else {

// Otherwise, iterate through all of the keys in the object.

for (k in value) {

if (Object.prototype.hasOwnProperty.call(value, k)) {

v = str(k, value);

if (v) {

partial.push(quote(k) + (

gap

? ": "
“:”

) + v);

}

}

}

}

// Join all of the member texts together, separated with commas,

// and wrap them in braces.

v = partial.length === 0

? “{}”
gap
? “{\n” + gap + partial.join(“,\n” + gap) + “\n” + mind + “}”
“{” + partial.join(“,”) + “}”;

gap = mind;

return v;

}

}

// If the JSON object does not yet have a stringify method, give it one.

if (typeof JSON.stringify !== “function”) {

meta = { // table of character substitutions

“\b”: “\b”,

“\t”: “\t”,

“\n”: “\n”,

“\f”: “\f”,

“\r”: “\r”,

“”“: “\””,

“\”: “\\”

};

JSON.stringify = function (value, replacer, space) {

// The stringify method takes a value and an optional replacer, and an optional

// space parameter, and returns a JSON text. The replacer can be a function

// that can replace values, or an array of strings that will select the keys.

// A default replacer method can be provided. Use of the space parameter can

// produce text that is more easily readable.

var i;

gap = “”;

indent = “”;

// If the space parameter is a number, make an indent string containing that

// many spaces.

if (typeof space === “number”) {

for (i = 0; i < space; i += 1) {

indent += " ";

}

// If the space parameter is a string, it will be used as the indent string.

} else if (typeof space === “string”) {

indent = space;

}

// If there is a replacer, it must be a function or an array.

// Otherwise, throw an error.

rep = replacer;

if (replacer && typeof replacer !== “function” &&

(typeof replacer !== “object” ||

typeof replacer.length !== “number”)) {

throw new Error(“JSON.stringify”);

}

// Make a fake root object containing our value under the key of “”.

// Return the result of stringifying the value.

return str(“”, {“”: value});

};

}

// If the JSON object does not yet have a parse method, give it one.

if (typeof JSON.parse !== “function”) {

JSON.parse = function (text, reviver) {

// The parse method takes a text and an optional reviver function, and returns

// a JavaScript value if the text is a valid JSON text.

var j;

function walk(holder, key) {

// The walk method is used to recursively walk the resulting structure so

// that modifications can be made.

var k;

var v;

var value = holder[key];

if (value && typeof value === “object”) {

for (k in value) {

if (Object.prototype.hasOwnProperty.call(value, k)) {

v = walk(value, k);

if (v !== undefined) {

value[k] = v;

} else {

delete value[k];

}

}

}

}

return reviver.call(holder, key, value);

}

// Parsing happens in four stages. In the first stage, we replace certain

// Unicode characters with escape sequences. JavaScript handles many characters

// incorrectly, either silently deleting them, or treating them as line endings.

text = String(text);

rx_dangerous.lastIndex = 0;

if (rx_dangerous.test(text)) {

text = text.replace(rx_dangerous, function (a) {

return “\u” +

(“0000” + a.charCodeAt(0).toString(16)).slice(-4);

});

}

// In the second stage, we run the text against regular expressions that look

// for non-JSON patterns. We are especially concerned with “()” and “new”

// because they can cause invocation, and “=” because it can cause mutation.

// But just to be safe, we want to reject all unexpected forms.

// We split the second stage into 4 regexp operations in order to work around

// crippling inefficiencies in IE’s and Safari’s regexp engines. First we

// replace the JSON backslash pairs with “@” (a non-JSON character). Second, we

// replace all simple value tokens with “]” characters. Third, we delete all

// open brackets that follow a colon or comma or that begin the text. Finally,

// we look to see that the remaining characters are only whitespace or “]” or

// “,” or “:” or “{” or “}”. If that is so, then the text is safe for eval.

if (

rx_one.test(

text

.replace(rx_two, “@”)

.replace(rx_three, “]”)

.replace(rx_four, “”)

)

) {

// In the third stage we use the eval function to compile the text into a

// JavaScript structure. The “{” operator is subject to a syntactic ambiguity

// in JavaScript: it can begin a block or an object literal. We wrap the text

// in parens to eliminate the ambiguity.

j = eval(“(” + text + “)”);

// In the optional fourth stage, we recursively walk the new structure, passing

// each name/value pair to a reviver function for possible transformation.

return (typeof reviver === “function”)

? walk({“”: j}, “”)
j;

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