How do I return an array of elements NOT in a Javascript map?

Question

I have a Javascript object:

var errorMap = {
    100: 'You must enter a name.',
    200: 'You must enter an address.',
    300: 'You must enter a DOB.'
}

In another part of my code, I am receiving an array of error codes:

var errorCodes = [100, 200, 500, 600];

What I'd like to do is compare the errorCodes array to the errorMap object's keys and return all error codes that do not have a corresponding key in errorMap. In this case, I would like to get this back:

[500, 600]

How do I do this? I have access to jQuery.

I am sure this is a duplicate, but I don't think of that question .. — user166390
– user166390, Commented Jul 11, 2012 at 19:42

Esailija · Accepted Answer · 2012-07-11 19:53:58Z

7

Javascript for modern browsers (works in older browsers with a shim)

var missing = [100, 200, 500, 600].filter(function(v){
    return !errorMap.hasOwnProperty(v)
});

//missing = [500, 600]

jQuery in case legacy browser support is required and shim is not acceptable:

var missing = $.grep( [100, 200, 500, 600], function(v){
    return !errorMap.hasOwnProperty(v)
});

//missing = [500, 600]

edited Jul 11, 2012 at 19:53

answered Jul 11, 2012 at 19:33

Esailija

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18 Comments

Rob W Over a year ago

Link to MDN docs, if anyone is wondering (includes polyfill, which is needed in IE8-).

ThiefMaster Over a year ago

Unless someone does incredibly nasty stuff (extending Object.prototype) there's nothing wrong with using in - and it's much more readable!

Esailija Over a year ago

@ThiefMaster agree. You can foolproof that with for( var key in Object.prototype ) throw new Error("pls die");

freakish Over a year ago

Remember that filter is no supported in older browser, in particular in IE8 (assuming there are living beings who care about it :] ).

Esailija Over a year ago

@freakish here's code for it developer.mozilla.org/en/JavaScript/Reference/Global_Objects/… We need to make developers more aware of these already 3 year old functions which work fine in ie7-8 with user code

|

ThiefMaster · Accepted Answer · 2012-07-11 19:32:26Z

1

jQuery is not really necessary, a simple for loop does the job, too:

var missing = [];
for(var i = 0; i < errorCodes.length; i++) {
    var code = errorCodes[i];
    if(errorMap[code] === undefined) {
        missing.push(code)
    }
});

With jQuery:

var missing = [];
$.each(errorCodes, function(i, code) {
    if(errorMap[code] === undefined) {
        missing.push(code)
    }
});

answered Jul 11, 2012 at 19:32

ThiefMaster

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4 Comments

Trufa Over a year ago

@Neal the question is tagged jQuery!

ThiefMaster Over a year ago

Exactly. Besides that, I just added a non-jQuery version.

freakish Over a year ago

@ThiefMaster: following your own comment: what if errorMap maps an error to undefined? The only way to do this is with hasOwnProperty.

ThiefMaster Over a year ago

that is really unlikely (well, ok, the empty string is also rather unlikely)

Naftali · Accepted Answer · 2012-07-11 19:32:40Z

0

var notRealError = [];
for(var i = 0; i < errorCodes.length; ++i){
    if(!errorMap[errorCodes[i]])  notRealError.push(errorCodes[i]);
}

notRealError is an array that contains the error codes that are not in your map.

answered Jul 11, 2012 at 19:32

Naftali

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1 Comment

Naftali Over a year ago

@ThiefMaster hmm that is true. but I am using the OP's definition of just using numbers.

freakish · Accepted Answer · 2012-07-11 19:33:19Z

0

No need for jQuery with this one. Try this:

var result = [];
var l = errorCodes.length;
for (var i = 0; i < l; i++)
    if (!errorMap.hasOwnProperty(errorCode[i]))
        result.push(errorCode[i]);

answered Jul 11, 2012 at 19:33

freakish

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Comments

Rocky Pulley · Accepted Answer · 2012-07-11 19:34:16Z

0

var returnCodes = [];

for (c in errorCodes) {
    if (errorMap[errorCodes[c]] == undefined) {
        returnCodes.push(errorCodes[c]);
    }
}

return returnCodes;

answered Jul 11, 2012 at 19:34

Rocky Pulley

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