Examples of efficient methods for converting Json strings into JS objects_javascript skills

Today I studied the JQuery source code and saw how to parse the JSON string like this:

Copy the code The code is as follows:

parseJSON: function( data ) {
if ( typeof data !== "string" || !data ) {
return null;
}

// Make sure leading/trailing whitespace is removed (IE can't handle it)
data = jQuery.trim( data );

// Make sure the incoming data is actual JSON
// Logic borrowed from http://json.org/json2.js
if ( /^[/],:{}/s]*$/.test(data.replace(///(? :["////bfnrt]|u[0-9a-fA-F]{4})/g, "@")
.replace(/"[^"///n/r]* "|true|false|null|-?/d (?:/./d*)?(?:[eE][ /-]?/d )?/g, "]")
.replace( /(?:^|:|,)(?:/s*/[) /g, "")) ) {

// Try to use the native JSON parser first
return window.JSON && window.JSON.parse ?
window.JSON.parse( data ) :
(new Function("return " data ))();

} else {
jQuery.error( "Invalid JSON: " data );
}
}

The core code of this method is:

Copy code The code is as follows:

(new Function("return " data))();

It uses the Function() constructor. The json string is passed in as function execution data, and the function is executed immediately after definition. At this time, this function will return a JSON object

I did a test and found that parsing JSON strings using this method is hundreds of times faster than using Eval

Copy code The code is as follows:

var jsonStr ="{";
for(var i=0;i<10000;i ){
jsonStr ="a" i ":" i ","
}
jsonStr = jsonStr.substring(0,jsonStr.length-1);
jsonStr ="}";

var date = new Date();
var start = date.getTime()
//var boj = (new Function("return " jsonStr ))();
var boj = eval ("(" jsonStr ")");
var date1 = new Date();
console.info(date1.getTime()-start);

I used firfox to test As a result, using eval to parse took 7234 milliseconds, while using the function method took 55 milliseconds, which is amazing.