More efficient way than using lots of else if statements

Question

I'm trying to find a better way to do this in Javascript:

if ( text === 'amy' ) {
var url = 'http://www.mydomain.com/amylikescats.html';
}
else if ( text === 'dave' ) {
var url = 'http://www.mydomain.com/daveshome.html';
}
else if ( text === 'steve' ) {
var url = 'http://www.mydomain.com/steve2.html';
}
else if ( text === 'jake' ) {
var url = 'http://www.mydomain.com/jakeeatstofu.html';
}
else {
var url = 'http://www.mydomain.com/noone.html';
}

Is there a more code efficient way of doing this?'

There are already some great answers below - this other stack overflow question is quite well referenced too and explains in a bit more depth: http://stackoverflow.com/a/2573153/649979 — Graham Smith, Aug 07 '12 at 10:53

score 14 · Accepted Answer · answered Aug 07 '12 at 10:51

14

Use an object as a map:

var map = {
    "amy": 'http://www.mydomain.com/amylikescats.html',
    "dave": 'http://www.mydomain.com/daveshome.html',
    // etc
};

var text = "whatever";
var url = map[text] === undefined ? 'http://www.mydomain.com/noone.html' : map[text];

This will save you the maximum amount of repeated code, but if you also need to do other stuff than setting url a switch might be more appropriate.

answered Aug 07 '12 at 10:51

Jon

428,835
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738
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If it's just a _mapping_ of keys to values, this is the best solution. – Aesthete Aug 07 '12 at 10:56

score 5 · Answer 2 · answered Aug 07 '12 at 10:50

Switch statement!

var url = 'http://www.mydomain.com/noone.html';
switch(text) {
  case 'amy': url = 'http://www.mydomain.com/amylikescats.html';
  break;
  case 'dave': url = 'http://www.mydomain.com/daveshome.html';
  break;
  case 'steve': url = 'http://www.mydomain.com/steve2.html';
  break;
  case 'jake': url = 'http://www.mydomain.com/jakeeatstofu.html';
  break;
}

Now there is no need for a default clause because you've initialized url before the switch.

Otherwise you could add this:

default: url = 'http://www.mydomain.com/noone.html';
break;

score 0 · Answer 3 · answered Aug 07 '12 at 10:52

0

Associative array:

var data = {
  amy: 'http://www.mydomain.com/amylikescats.html',
  dave: 'http://www.mydomain.com/daveshome.html',
  // etc... 
}

To use:

var url = data[text];

The else case can be replicate dby the non-existance of the item in the array, so expanding a bit:

var url = '';
if(!(text in data)){
    url = 'http://www.mydomain.com/daveshome.html';
}
else{
    url = data[text];
}

answered Aug 07 '12 at 10:52

Jamiec

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In JavaScript, they’re called objects. – Paul D. Waite Aug 07 '12 at 10:58
@PaulD.Waite - pedantic much? [This goog search](https://www.google.co.uk/search?q=javascript+associative+array&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a) indicates that the term "associative array" is quite often linked with javascript (judging by the ~400K results). – Jamiec Aug 07 '12 at 11:23
True true, and the concept of an associative array (if I understand properly) perfectly applies to JavaScript objects. It’s just not what they’re called in JavaScript. – Paul D. Waite Aug 07 '12 at 11:51

score 0 · Answer 4 · answered Aug 07 '12 at 10:52

Store the unique parts in a dictionary and then take it from there:

var map = {
    amy: "amylikescats",
    dave: "daveshome",
    steve: "steve2",
    jake: "jakeeatstofu"
};
var url = map[text];
if (!url) {
    url = 'http://www.mydomain.com/noone.html';
} else {
    url = 'http://www.mydomain.com/' + url + '.html';
}

Paul D. Waite · Answer 5 · 2012-08-07T11:51:57.320

You could use an object to hold the URLs for different values of text, and then use the || operator when assigning a value to url to use the fallback value if necessary.

var urlsForText = {
      'amy': 'http://www.mydomain.com/amylikescats.html',
     'dave': 'http://www.mydomain.com/daveshome.html',
    'steve': 'http://www.mydomain.com/steve2.html',
     'jake': 'http://www.mydomain.com/jakeeatstofu.html'
};

var url = urlsForText[text] || 'http://www.mydomain.com/noone.html';

More efficient way than using lots of else if statements

5 Answers5