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Evaluating JavaScript

Evaluate a string of JavaScript statements​

var x = 5;
var str = "if (x == 5) {console.log('z is 42'); z = 42;} else z = 0; ";
console.log("z is ", eval(str));

The use of eval is strongly discouraged. See the Remarks section for details.

Introduction​

You can always run JavaScript from inside itself, although this is strongly discouraged due to the security vulnerabilities it presents (see Remarks for details).

To run JavaScript from inside JavaScript, simply use the below function:

eval("var a = 'Hello, World!'");

Evaluation and Math​

You can set a variable to something with the eval() function by using something similar to the below code:

var x = 10;
var y = 20;
var a = eval("x * y") + "<br>"; 
var b = eval("2 + 2") + "<br>"; 
var c = eval("x + 17") + "<br>";
var res = a + b + c;

The result, stored in the variable res, will be:

200
4
27

The use of eval is strongly discouraged. See the Remarks section for details.