eval javascript code example

Example 1: Calculate string value in javascript, not using eval

let str = "12/5*9+9.4*2"

let res1 = eval(str)
console.log('res1:', res1)

let res2 = (new Function('return '+str)())
console.log('res2:', res2)

Example 2: javascript execute string code

var theInstructions = "alert('Hello World'); var x = 100";

var F=new Function (theInstructions);

return(F());

Example 3: what is eval in js

The eval() function evaluates JavaScript code represented as a string.

console.log(eval('2 + 2'));
// expected output: 4

console.log(eval(new String('2 + 2')));
// expected output: 2 + 2

console.log(eval('2 + 2') === eval('4'));
// expected output: true

console.log(eval('2 + 2') === eval(new String('2 + 2')));
// expected output: false

Example 4: eval in javascript

eval() -> is able to evalute the things inside it , like eval(a+b+c) , wher a=3,b=4,c=4 , so eval(a+b+c) = 11

Example 5: eval javascript

eval(string)

Example 6: calculate string value in javascript

let res2 = (new Function('return '+str)())