In javascript, how do you search an array for a substring match

Question

If you're able to use Underscore.js in your project, the _.filter() array function makes this a snap:

// find all strings in array containing 'thi'
var matches = _.filter(
    [ 'item 1', 'thing', 'id-3-text', 'class' ],
    function( s ) { return s.indexOf( 'thi' ) !== -1; }
);

The iterator function can do whatever you want as long as it returns true for matches. Works great.

Update 2017-12-03:
This is a pretty outdated answer now. Maybe not the most performant option in a large batch, but it can be written a lot more tersely and use native ES6 Array/String methods like .filter() and .includes() now:

// find all strings in array containing 'thi'
const items = ['item 1', 'thing', 'id-3-text', 'class'];
const matches = items.filter(s => s.includes('thi'));

Note: There's no <= IE11 support for String.prototype.includes() (Edge works, mind you), but you're fine with a polyfill, or just fall back to indexOf().

People here are making this waaay too difficult. Just do the following...

myArray.findIndex(element => element.includes("substring"))

findIndex() is an ES6 higher order method that iterates through the elements of an array and returns the index of the first element that matches some criteria (provided as a function). In this case I used ES6 syntax to declare the higher order function. element is the parameter of the function (which could be any name) and the fat arrow declares what follows as an anonymous function (which does not need to be wrapped in curly braces unless it takes up more than one line).

Within findIndex() I used the very simple includes() method to check if the current element includes the substring that you want.

The simplest way to get the substrings array from the given array is to use filter and includes:

myArray.filter(element => element.includes("substring"));

The above one will return an array of substrings.

myArray.find(element => element.includes("substring"));

The above one will return the first result element from the array.

myArray.findIndex(element => element.includes("substring"));

The above one will return the index of the first result element from the array.

In your specific case, you can do it just with a boring old counter:

var index, value, result;
for (index = 0; index < windowArray.length; ++index) {
    value = windowArray[index];
    if (value.substring(0, 3) === "id-") {
        // You've found it, the full text is in `value`.
        // So you might grab it and break the loop, although
        // really what you do having found it depends on
        // what you need.
        result = value;
        break;
    }
}

// Use `result` here, it will be `undefined` if not found

But if your array is sparse, you can do it more efficiently with a properly-designed for..in loop:

var key, value, result;
for (key in windowArray) {
    if (windowArray.hasOwnProperty(key) && !isNaN(parseInt(key, 10))) {
        value = windowArray[key];
        if (value.substring(0, 3) === "id-") {
            // You've found it, the full text is in `value`.
            // So you might grab it and break the loop, although
            // really what you do having found it depends on
            // what you need.
            result = value;
            break;
        }
    }
}

// Use `result` here, it will be `undefined` if not found

Beware naive for..in loops that don't have the hasOwnProperty and !isNaN(parseInt(key, 10)) checks; here's why.

---

Off-topic:

Another way to write

var windowArray = new Array ("item","thing","id-3-text","class");

is

var windowArray = ["item","thing","id-3-text","class"];

...which is less typing for you, and perhaps (this bit is subjective) a bit more easily read. The two statements have exactly the same result: A new array with those contents.

Just search for the string in plain old indexOf

arr.forEach(function(a){
    if (typeof(a) == 'string' && a.indexOf('curl')>-1) {
            console.log(a);
    }        
});

The simplest vanilla javascript code to achieve this is

var windowArray = ["item", "thing", "id-3-text", "class", "3-id-text"];
var textToFind = "id-";

//if you only want to match id- as prefix 
var matches = windowArray.filter(function(windowValue){
  if(windowValue) {
      return (windowValue.substring(0, textToFind.length) === textToFind);
  }
}); //["id-3-text"]

//if you want to match id- string exists at any position
var matches = windowArray.filter(function(windowValue){
  if(windowValue) {
      return windowValue.indexOf(textToFind) >= 0;
  }
}); //["id-3-text", "3-id-text"]

For a fascinating examination of some of the alternatives and their efficiency, see John Resig's recent posts:

• JavaScript Trie Performance Analysis
• Revised JavaScript Dictionary Search

(The problem discussed there is slightly different, with the haystack elements being prefixes of the needle and not the other way around, but most solutions are easy to adapt.)