This site is mobile accessible. Press the "Tap Here" button to use a smaller font-size. Tap Here!

Smartphone icons created by Freepik - Flaticon

JS Variables

Remove the comment (at the beginning of the lines) to test each case:

let x = 5;
//x = 5 + 7;    // x.valueOf() is 12, typeof x is a number
x = 5 + "7";  // x.valueOf() is 57, typeof x is a string
//x = "5" + 7;  // x.valueOf() is 57, typeof x is a string
//x = 5 - 7;    // x.valueOf() is -2, typeof x is a number
//x = 5 - "7";  // x.valueOf() is -2, typeof x is a number
//x = "5" - 7;  // x.valueOf() is -2, typeof x is a number
//x = 5 - "x";  // x.valueOf() is NaN, typeof x is a number

document.getElementById("demo").innerHTML = x.valueOf() + " " + typeof x;