Javascript array search

Question

Whats the best way to search a javascript array for an entry?? All the items will be strings.

Is it simply by using lastIndexOf? like so:

var list= [];
list.push("one");
list.push("two");
list.push("three");
if(list.lastIndexOf(someString) != -1)
{
 alert("This is already present in list");
 return;
}

• Matt Zeunert: Do you need all occurrences? What doesn't work about lastIndexOf?

Answer 1

Is it simply by using lastIndexOf?

Yes. However, I'd use even simpler indexOf() if you don't need to explicitly search backwards (which you don't if you test for "does not contain"). Also notice that these methods were standardized in ES5 and need to be shimmed in old browsers that do not support them natively.

• Mulan: @MikeCorcoran he specifically said it needs to be shimmed in older browsers.

Answer 2

For older browser support, you should still use a loop:

function inArray(arrToSearch, value) {
 for (var i=0; i < arrToSearch.length; i++) {
 if (arrToSearch[i] === value) {
 return true;
 }
 }
 return false;
};

Answer 3

You can try the build in array method of javascript find. It's the easiest way for your problem. Here is the code:

var list = [], input = "two";
list.push("one");
list.push("two");
list.push("three");
function match(element){
 return element == input;
}
if(list.find(match)){
 console.log('Match found');
}

Answer 4

var arr = ["one","two","three"];
Array.prototype.find = function(val){
 for(var i = 0; i < this.length; i++) {
 if(this[i] === val){
 alert("found");
 return;
 }
 }
 alert("not found");
}
arr.find("two");

Should work in most older browsers.

https://jsfiddle.net/t73e24cp/

• Mulan: Array.prototype.find is an actual thing in future ECMAScript. I don't recommend naming the function that.
• Mulan: It's right around the corner (developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…); Firefox and Safari already have it implemented.
• brroshan: Thanks for the info :) I didn't know