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    JSON.parse()

    Summary

    The JSON.parse() method parses a string as JSON, optionally transforming the value produced by parsing.

    Syntax

    JSON.parse(text[, reviver])

    Parameters

    text
    The string to parse as JSON. See the JSON object for a description of JSON syntax.
    reviver Optional
    If a function, prescribes how the value originally produced by parsing is transformed, before being returned.

    Returns

    Returns the Object corresponding to the given JSON text.

    Exceptions

    Throws a SyntaxError exception if the string to parse is not valid JSON.

    Examples

    Example: Using JSON.parse()

    JSON.parse('{}');              // {}
    JSON.parse('true');            // true
    JSON.parse('"foo"');           // "foo"
    JSON.parse('[1, 5, "false"]'); // [1, 5, "false"]
    JSON.parse('null');            // null
    

    Example: Using the reviver parameter

    If a reviver is specified, the value computed by parsing is transformed before being returned. Specifically, the computed value, and all its properties (beginning with the most nested properties and proceeding to the original value itself), are individually run through the reviver, which is called with the object containing the property being processed as this and with the property name as a string and the property value as arguments. If the reviver function returns undefined (or returns no value, e.g. if execution falls off the end of the function), the property is deleted from the object. Otherwise the property is redefined to be the return value.

    The reviver is ultimately called with the empty string and the topmost value to permit transformation of the topmost value. Be certain to handle this case properly, usually by returning the provided value, or JSON.parse will return undefined.

    JSON.parse('{"p": 5}', function (k, v) {
        if(k === "") return v;     // if topmost value, return it,
        return v * 2;              // else return v * 2.
    });                            // { p: 10 }
    
    JSON.parse('{"1": 1, "2": 2,"3": {"4": 4, "5": {"6": 6}}}', function (k, v) {
        console.log(k);            // log the current property name, the last is "".
        return v;                  // return the unchanged property value.
    });
    
    // 1
    // 2
    // 4
    // 6
    // 5
    // 3 
    // ""
    

    Specifications

    Specification Status Comment
    ECMAScript 5.1 (ECMA-262)
    The definition of 'JSON.parse' in that specification.
    Standard Initial definition.
    Implemented in JavaScript 1.7.
    ECMAScript 6 (ECMA-262)
    The definition of 'JSON.parse' in that specification.
    Draft  

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support (Yes) 3.5 (1.9.1) 8.0 10.5 4.0
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support (Yes) (Yes) 1.0 (1.0) (Yes) (Yes) (Yes)

    Based on Kangax's compat table.

    Gecko-specifc notes

    • Starting Gecko 29 (Firefox 29 / Thunderbird 29 / SeaMonkey 2.26), a malformed JSON string yields a more detailed error message containing the line and column number that caused the parsing error. This is useful when debugging large JSON data.
      JSON.parse('[1, 2, 3,]')
      // SyntaxError: JSON.parse: unexpected character at line 1 column 10 of the JSON data
      

    See also

    Document Tags and Contributors

    Last updated by: ziyunfei,