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up vote 0 down vote favorite

I have such an array:

arr['key1'] = true;
arr['key2'] = true;
arr['key3'] = true;
...
arr['keyN'] = true;

How to determine, have anyone key a "false" value?

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1  
Possibly duplicate: stackoverflow.com/questions/143847 (may not work when looking for true and false though). – Felix Kling Apr 7 '10 at 10:29
1  
Why is this a CW? – T.J. Crowder Apr 7 '10 at 10:29
1  
If you have an array you shouldn't be using non-numeric properties on it. If you need non-numeric properties, use a plain object. – Quentin Apr 7 '10 at 10:33
Felix, can you answer, that to i can flag your answer like a decision. – Ax. Apr 7 '10 at 10:45

4 Answers

up vote 7 down vote accepted

Unfortunately, the only way to do this until recently was to loop through the array; if you're using this in a browser-based app, you'll probably have to do it that way. There are new array features in ECMAScript 5th edition (the new JavaScript) that let you do this in a slightly different way, but only some browsers support them (and I'm not sure they'd necessarily be applicable).

But what you've described in your question is more a map (or "dictionary;" sometimes called an associative array) than an array (numerically-based indexed thingy). In JavaScript, "array" is usually used to mean numerically-indexed arrays (e.g., created via [] or new Array), and "object" is usually used for maps (because all JavaScript objects are maps). (This can be a bit confusing, because arrays are objects. But don't worry about that.) So this is an array:

var a = ['one', 'two', 'three'];

...whereas this is an object ("map", "dictionary", "associative array"):

var o = {key1: 'one', key2: 'two', key3: 'three'};

Your use of non-numeric indexes suggests you're really using a map, not an array. The search loop looks something like this on maps:

var key, found;

found = false;
for (key in arr) {
    if (arr.hasOwnProperty(key)) {
        if (!arr[key]) {   // <== There are alternatives, see notes below
            found = true;
            break;
        }
    }
}

There I've used if (!arr[key]) to check for the false value. That will actually stop on false, undefined, null, or an empty string. If you really, really want false, use if (arr[key] === false) instead.

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up vote 0 down vote
  1. loop through each value in the array (for-loop)
  2. check the value to see if it's false.

are you new to Javascript?

for(var i = 0; i < arr.length; i++) {
    if(arr[i] === false) {
        // do something
    }
}
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2  
No need to be sarky, he's probably wondering if there's a built-in array function that will do it for him. Not an unreasonable thing to hope for. – T.J. Crowder Apr 7 '10 at 10:32
@TJ, Looping through an array is always a couple of examples away from "Hello World". So no, I'm not being sarcastic. – Anurag Apr 7 '10 at 10:40
Not, i'm not new in JS. But i finding way to not write myself if there is found decision. – Ax. Apr 7 '10 at 10:42
@Anurag: Reads sarcastic to me (and apparently someone else, but just one someone else). (Edit: Okay, so now it's two other people.) – T.J. Crowder Apr 7 '10 at 10:42
@Ax.. there are some great answers available here. I suggest you start with simple answers, and test all others from there. If you want an online tool to quickly test a piece of Javascript code, then checkout jsfiddle.com – Anurag Apr 7 '10 at 11:04
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up vote 2 down vote 
function hasFalse(arr) {
    for (i in arr) {
        if (!arr[i]) {
            return true;
        }
    }
    return false;
}

This returns as soon as a single false is found.

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up vote 3 down vote 
for(key in arr){
  var value = arr[key];
  if(!value){
    //do stuff
  }
}
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