eval mdn 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());