Check if string begins with something? [duplicate]

Answer 1

First, lets extend the string object. Thanks to Ricardo Peres for the prototype, I think using the variable 'string' works better than 'needle' in the context of making it more readable.

String.prototype.beginsWith = function (string) {
    return(this.indexOf(string) === 0);
};

Then you use it like this. Caution! Makes the code extremely readable.

var pathname = window.location.pathname;
if (pathname.beginsWith('/sub/1')) {
    // Do stuff here
}

Answer 2

Use stringObject.substring

if (pathname.substring(0, 6) == "/sub/1") {
    // ...
}

Answer 3

You can use string.match() and a regular expression for this too:

if(pathname.match(/^\/sub\/1/)) { // you need to escape the slashes

string.match() will return an array of matching substrings if found, otherwise null.

Answer 4

A little more reusable function:

beginsWith = function(needle, haystack){
    return (haystack.substr(0, needle.length) == needle);
}

Answer 5

String.prototype.startsWith = function(needle)
{
    return this.indexOf(needle) === 0;
};

Answer 6

Have a look at JavaScript substring() method.