String available check in for loop

Question

I have these cat breeds

cats = [
'Abyssinian',
'Balinese',
'Bombay',
'Birman'];

Now the code written is generally something like this

 for(var i in cats)
 {
  ... do
 }

Now I have to modify the same function in javascript. I can only modify to see if i is any of Balinese or Bombay .. then do these

I am thinking

 for(var i in cats)
 {
  if(i == 'Balinese' || i == 'Bombay'){
  ... do
  }
 }

Instead I would like something like i contains Balinese,Bombay instead of writing the | clause in middle?

 for(var i in cats)
 {
  if(i.contains('Balinese', 'Bombay'){   //this would be better, suggestions?
  ... do
  }
 }

How?

http://stackoverflow.com/questions/237104/array-containsobj-in-javascript — CD.., Jun 27 '12 at 08:12
Also you need to mention type of your cat breeds if they are in array or object literal — Blaster, Jun 27 '12 at 08:12
`cats{ Abyssinian, Balinese, Bombay, Birman}` isn't valid syntax, seeing that all that follows builds on that, it's hard to guess which error you're trying to fix. — Yoshi, Jun 27 '12 at 08:17
I don't quite understand why the logical OR operator is that much of a disturbance to you. — Octavian Helm, Jun 27 '12 at 08:18
If jQuery is an option, this all comes down to about one line of code. http://api.jquery.com/jQuery.inArray/ — DACrosby, Jun 27 '12 at 08:25

Jashwant · Answer 1 · 2012-06-27T08:56:55.193

Try this code,

This adds the .indexOf() in non-supported browsers

if (!Array.prototype.indexOf) {  
    Array.prototype.indexOf = function (searchElement /*, fromIndex */ ) {  
        "use strict";  
        if (this == null) {  
            throw new TypeError();  
        }  
        var t = Object(this);  
        var len = t.length >>> 0;  
        if (len === 0) {  
            return -1;  
        }  
        var n = 0;  
        if (arguments.length > 0) {  
            n = Number(arguments[1]);  
            if (n != n) { // shortcut for verifying if it's NaN  
                n = 0;  
            } else if (n != 0 && n != Infinity && n != -Infinity) {  
                n = (n > 0 || -1) * Math.floor(Math.abs(n));  
            }  
        }  
        if (n >= len) {  
            return -1;  
        }  
        var k = n >= 0 ? n : Math.max(len - Math.abs(n), 0);  
        for (; k < len; k++) {  
            if (k in t && t[k] === searchElement) {  
                return k;  
            }  
        }  
        return -1;  
    }  
}

Adding contains method in Array prototype

 Array.prototype.contains = function(){ 
       for(var i=0,len=arguments.length;i<len;i++){
          if(this.indexOf(arguments[i]) !== -1){ 
              return true;
          } 
       }
       return false;
    }

Now, you can use like this,

var cats = [
'Abyssinian',
'Balinese',
'Bombay',
'Birman'];

if(cats.contains('Balinese')){
  console.log('Balinese');
}

if(cats.contains('Balinese','Bombay')){
  console.log('Balinese,Bombay');
}

if(cats.contains('lines','Bombay')){
  console.log('lines,Bombay');
}

if(cats.contains('lines','mbay')){
  console.log('lines,mbay');
}

If you are using jQuery, this code can be made simpler :)

DACrosby · Answer 2 · 2012-06-27T09:17:09.527

0

Try nested loops?

var cats = ["Abyssinian", "Balinese", "Bombay", "Birman"];
var thisAndThat = ["Abyssinian", "Apple", "Siberian", "Windows", "StackOverflow"];

for(var i in cats) {
    for(var x in thisAndThat) {
        if(cats[i] == thisAndThat[x]){
            ... do
        }
    }
}

With jQuery

$.each(thisAndThat, function(key, value){
  if( $.inArray(value, cats) > -1 ){
    alert(value+" is inside the cats array.");
  }
});

edited Jun 27 '12 at 09:17

answered Jun 27 '12 at 08:17

DACrosby

11,116
3
39
51

Your array initialisation is wrong. Not `var cats[] = [a,b,c];` , but `var cats = [a,b,c];` – Jamiec Jun 27 '12 at 08:30
Oh man, this just isn't my day for JavaScript syntax. Thanks for catching that! – DACrosby Jun 27 '12 at 08:57

score 0 · Answer 3 · answered Jun 27 '12 at 08:24

check this code,

var cats=['Abyssinian', 'Balinese', 'Bombay', 'Birman'];

Array.prototype.contains=function(incattype){

    for(var i=0; i<cats.length;i++){

        if(cats[i]==incattype) {
            return true;
        } else{
             return false;
        }      
    }
};


  var catslist=['Abyssinian', 'Balinese', 'Bombay11' ];

    for(var i=0; i<catslist.length;i++){

        document.write(cats.contains(catslist[i]));
    }

link;-

http://jsfiddle.net/fPdej/2/

why build a contains method, when there already is an [`indexOf`](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/indexOf)-method? — Yoshi, Jun 27 '12 at 08:25

score 0 · Answer 4 · edited May 23 '17 at 10:09

First off, its important to realise that if you are traversing a javascript array with for...in then it is imperative that you use the hasOwnProperty method:

for(var i in cats){
    if(cats.hasOwnProperty(i))
        console.log(cats[i]);        
}

You really should be using for(;;) like so:

for(var i=0;i<cats.length;i++){
   console.log(cats[i]);
}

All that aside, you are looking for Array.indexOf, which is supported by modern browser but may have less support in older browsers - this is why most frameworks (jQuery, Moo, prototype etc) define their own variant of this method (See this question's answers for more detail).

var cats = ["Abyssinian","Balinese","Bombay","Birman"];

var test = ["Abyssinian","Balinese"];

for(var i in cats){
    if(cats.hasOwnProperty(i) && test.indexOf(cats[i]) != -1)
        console.log(cats[i]);        
}

Live example: http://jsfiddle.net/4xJsg/

score 0 · Answer 5 · answered Jun 27 '12 at 08:32

It's not recomended to use for-in loops, because they are up to seven times slower than for, while or do-while ones. Instead of for-in, you can use for-each, too, which is not as faster as for or while but is more similar to for-in loops.

Combining it with regular expressions, my approach is:

var cats = [
    'Abyssinian',
    'Balinese',
    'Bombay',
    'Birman'
];

cats.forEach(function(cat, index){
    if(cat.match(/Abyssinian|Birman/)){
    // Do what you want
    }
});

String available check in for loop

5 Answers5