javascript - Is there a shortcut syntax for checking types of variables? - Stack Overflow

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In JavaScript, how do I say:

if (typeof obj === 'number' 
    || typeof obj === 'boolean' 
    ||  typeof obj === 'undefined' 
    || typeof obj === 'string') {

In other words, is there some kind of:

if (typeof obj in('number','boolean','undefined','string')) {

In JavaScript, how do I say:

if (typeof obj === 'number' 
    || typeof obj === 'boolean' 
    ||  typeof obj === 'undefined' 
    || typeof obj === 'string') {

In other words, is there some kind of:

if (typeof obj in('number','boolean','undefined','string')) {

• javascript

Share Improve this question Follow edited Jul 5, 2011 at 23:39 user456814 asked Jul 5, 2011 at 23:35 Phillip SennPhillip Senn 47.7k9191 gold badges261261 silver badges378378 bronze badges 2

• Are you looking to improve on the first statement? – Declan Cook Commented Jul 5, 2011 at 23:39
• Just curious -- why do you need to check for so many types? I've never had to do this before. – Casey Chu Commented Jul 6, 2011 at 4:13

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5 Answers 5

Sorted by: Reset to default 6

You can use a switch:

switch (typeof obj) {
  case 'number':
  case 'boolean':
  case 'undefined':
  case 'string':
    // You get here for any of the four types
    break;
}

In Javascript 1.6:

if (['number','boolean','undefined','string'].indexOf(typeof obj) !== -1) {
  // You get here for any of the four types
}

You could approximate it with something like

var acceptableTypes = {'boolean':true,'string':true,'undefined':true,'number':true};

if ( acceptableTypes[typeof obj] ){
  // whatever
}

or the more verbose

if ( typeof obj in acceptableTypes){
  // whatever
}

Yes there is. typeof(obj) just returns a string, so you can simply do as you would when checking if a string is in any set of strings:

if (typeof(obj) in {'number':'', 'boolean':'', 'undefined':'', 'string':''})
{
  ...
}

Or you could make it even shorter. Since the only "types" that typeof may return are number, string, boolean object, function and undefined, in this particular case, you could just make an exclusion instead.

if (!(typeof(obj) in {'function':'', 'object':''}))
{
  ...
}

More grist for the mill:

if ( ('object function string undefined').indexOf(typeof x) > -1) {
  // x is an object, function, string or undefined
}

or

if ( (typeof x).match(/object|function|string|undefined/)) {
  // x is an object, function, string or undefined
}

How many ways do you want this cat skinned?

I like to use functional programming for similar situations. So you can use underscore.js to make it more readable:

_.any(['number','boolean','undefined','string'], function(t) {
  return typeof(obj) === t; 
});

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