Check for a value in Array

Question

I'm trying to check for match in an array with PURE JAVASCRIPT. I don't know how to do this, I would appreciate your help.

var sites = new Array ("site1.com", "site2.com", "site3.com" ...);
// Sites array contains 100 values

var imgs = document.getElementsByTagName("img");
    for (var i = 0; i < imgs.length; i++) {
        img = imgs[i].src;

        // I'm trying to check if is in array, 
        // and don't waste a lot of size in code

        if(img.match(sites)){
            notHere(imgs[i]);
        }

        // This is the working way.
        // Even if location is a.site1.com/b/, it will match 
        if (img.match("site1.com")) {
            heReload(imgs[i]);
        }
        // Repeat this piece of code 100 times
    }
}

NOTE: I don't want to check for an exact value. I want to simulate the match() function so if img = "http://a.b.c/d/" and in array is "b.c/", it executes function().

georg · Accepted Answer · 2012-04-30 15:14:00Z

1

Your "sites" variable should be a regular expression rather than an array:

 var sites = /\b(site1\.com|site2\.com|etc|etc)\b/

later:

 if (img.match(sites))
    ......

If for some reason you prefer to keep "sites" in an array, you also can create a regular expression "on the fly":

var sites = ["site1.com", "site2.com", "site3.com"]
var sitesRegexp = new RegExp("\\b(" + sites.join("|").replace(".", "\\.") + ")\\b")

 ....

 if (img.match(sitesRegexp)
    ......

answered Apr 30, 2012 at 15:14

georg

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1 Comment

Rob W Over a year ago

Do not forget to escape special RegEx characters! A dot is not the only special character. .replace(/[[^$.|?*+(){}\\]/g, '\\$&');

Jérémie Parker · Accepted Answer · 2012-04-30 15:40:57Z

Good use case for filter.

If you want to have it working on "old" browser :

var nativeFilter = Array.prototype.filter;
_.filter = _.select = function(obj, iterator, context) {
    var results = [];
    if (obj == null) return results;
    if (nativeFilter && obj.filter === nativeFilter) return obj.filter(iterator, context);
    each(obj, function(value, index, list) {
      if (iterator.call(context, value, index, list)) results[results.length] = value;
    });
    return results;
};

It will return an empty array if nothing is found, otherwise, return an array containing the result(s)

> [1,2,3,4].filter(function(item) { return item == 4 } );
[ 4 ]

Source : Underscore.js

So now your code will look like this :

var sites = new Array ("site1.com", "site2.com", "site3.com" ...);
// Sites array contains 100 values

var imgs = document.getElementsByTagName( "img" );
for ( var i = 0; i < imgs.length; i++ ) {
    var img = imgs[ i ].src;
    var result = sites._filter( function( site ) {
        return img.match( site )
    });

    // result is an array of matching sites

}

Royi Namir · Accepted Answer · 2012-04-30 15:26:17Z

0

you can extend the Array prototype , so it supports all browsers ...

try this :

Array.prototype.myContains = function(obj) {
    var i = this.length;
    while (i--) {if (this[i] .indexOf(obj)>-1)  return true; }
    return false;
}

usage : var t=myArr.myContains(3);

edited Apr 30, 2012 at 15:26

answered Apr 30, 2012 at 15:18

Royi Namir

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