How to make 0 not equal to empty string in JavaScript

Question

I know the rules that 0 is equal to empty string '' in javascript. So how to make if statement to differ this? I mean, I have field where I insert amount value. For empty string I need one message to show but for 0 value another. Currently, I always catch 0 == ''.

    if (amount == '') {
       $("#validation-msg3").addClass("opux-is-visible");

       return false;
    }
    else if (amount < 5) {
        $("#validation-msg1").addClass("opux-is-visible");

        return false;
    }

EDIT. when I use === I do not get condition equals true when field is empty. What does it mean? My amount value is different type than empty string? I parse it like this:

var amount = parseInput($("#amount").val());

This will help you: https://stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons — Mayday, Jun 13 '17 at 12:06
But now when I use `===` I do not get condition equals true when field is empty. What does it mean? My amount value is different type than empty string? I parse it like this: `var amount = parseInput($("#amount").val());` — Łukasz Bocheński, Jun 13 '17 at 12:14

score 2 · Answer 1 · answered Jun 13 '17 at 12:06

2

Just use strict compare === that will check value AND type of operands.

answered Jun 13 '17 at 12:06

Justinas

41,402
5
66
96

thanks but you didn't help – Łukasz Bocheński Jun 13 '17 at 13:06

score 1 · Answer 2 · answered Jun 13 '17 at 12:06

1

Use three equation signs. It checks the type too and 0 will be different from ''.

if (amount === '') {
   $("#validation-msg3").addClass("opux-is-visible");

   return false;
}

answered Jun 13 '17 at 12:06

JuhG

140
10

thanks but you didn't help – Łukasz Bocheński Jun 13 '17 at 13:06

How to make 0 not equal to empty string in JavaScript

2 Answers2