About new function use

has been to function () smattering, today on the use of function () to do a summary

The function is actually a fully functional object, and the function is created directly with Fucntion ().

Syntax rules:
var function name = new function (arg1, arg2, Arg3, ..., ArgN, body);
Explain:
Function constructors All arguments are string types, and body is the body of the generated function.

Example: To find multiple parameters and

var New Function (                 ' var = 0,args = Arguments;for (var i = 0; i < args.length; i++) {Total + = args[i];} return total; '  );             var res = fnsum (4,5,6);            Alert (res);

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Note: The above code is not allowed to have spaces

To improve the above wording

First notation (Traditional): Splitting a string

var New  Function (                ' var = 0, ' +                '    args = arguments; ' +                 ' for (var i = 0; i < args.length; i++) {' +                ' total    + = args[i]; ' + '                } ' +                ' return total; '            );             var res = fnsum (1,2,3,4 );            Alert (res); // Ten

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The second way: absorbing the idea of MVC

<script id= "Engin" >/*var total = 0, args = arguments, Len = args.length;                for (var i = 0; i < len; i++) {Total + = args[I]; } return total;*/</script> <script>varGetBody =function(ID) {varScript =document.getElementById (ID); varBODY = Script.innerHTML.replace ('/* ', '). Replace (' * * ', ' ');            Script.parentNode.removeChild (script); returnbody; } onload=function () {                                varFnsum =NewFunction (GetBody (' Engin ' ) ); varres = Fnsum (1, 2, 3 );    Alert (res); //6};

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Both function and eval can implement string execution code in real development, if you consider efficiency you can use eval directly, but considering security it is recommended to use Function

var str = ' {name: ' jim '} 'var o = ' + str'//var o = eval (' (' + str + ') '); In the sentence console.log (o); // Object {name: "Jim"}

Eval (' var a = ten; ');  // eval will contaminate global variables   var a = 10; // Global Variables

eval()is a top-level function and is not related to any object.

eval()The argument is a string. If the string represents an expression,eval () will execute the declaration. Do not call

If you want to construct an arithmetic expression into a string, you can use 3 * x + 2 ", as a variable, by calling

如果参数不是字符串，eval () 将会将参数原封不动的返回。 in the following example, the string constructor is specified, andeval () returns a String object instead of a string evaluation.

eval()is a dangerous function that can invoke code just like the power of a caller. If you use a string to runeval () then your code may be affected by malicious parties (hostile people), and by using malicious code on the user's machine, you may lose access to the Web page or extension  https://developer.mozilla.org/zh-cn/docs/ Web/javascript/reference/global_objects/eval

About new function use