Consider lookup tables instead of switch or if/else
There are a couple of methods to make distinctions between different possibilities. You can use if-else clauses:
function ifElseTest(stuff) {
if(stuff === "pizza") {
return "food";
} else if (stuff === "house") {
return "building";
} else if (stuff === "air") {
return "nothing";
}
};Or switch:
function switchTest(stuff) {
switch (stuff) {
case "pizza":
return "food";
break;
case "house":
return "building";
break;
case "air":
return "nothing";
break;
}
};But there is a possible faster one (http://jsperf.com/if-switch-lookup-table/1) – a simple lookup table in the form of an object:
var lookupTable = {
"pizza": function() {
return "food";
},
"house": function() {
return "building";
},
"air": function() {
return "nothing";
}
};just call
lookupTable["condition"]()to choose your wished conclusion.
Update:
For sure you should use this technique carefully. It's not always the best solution. Especially when you deal with integer conditions instead of strings (see http://coderwall.com/p/doeskg).
Written by Tobias Otte
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5 Responses
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Is there a simple way of initializing the lookup table from an external file?
Hi there,
1) Why are you using functions in the looking table.
Why not
var lookupTable = {
"pizza": "food",
"house": "building",
"air": "nothing",
};
console.log(lookupTable[condition]);
???
2) No default value in your examples.
In real life you'll have one generally. In this case, the lookup table is less efficient because you have to test the return value.
@Polatouche The function does not have to be returning a string. This is just an example. The function could be as complex as you like.
In the case of integer conditions, particularly consecutive, you could just use a lookup array.