Comparing strings lexicographically

To compare strings alphabetically, use localeCompare(). This returns a negative value if the reference string is lexicographically (alphabetically) before the compared string (the parameter), a positive value if it comes afterwards, and a value of 0 if they are equal.

var a = "hello";
var b = "world";

console.log(a.localeCompare(b)); // -1

The > and < operators can also be used to compare strings lexicographically, but they cannot return a value of zero (this can be tested with the == equality operator). As a result, a form of the localeCompare() function can be written like so:

function strcmp(a, b) {
    if(a === b) {
        return 0;
    }

    if (a > b) {
        return 1;
    }

    return -1;
}

console.log(strcmp("hello", "world")); // -1
console.log(strcmp("hello", "hello")); //  0
console.log(strcmp("world", "hello")); //  1

This is especially useful when using a sorting function that compares based on the sign of the return value (such as sort).

var arr = ["bananas", "cranberries", "apples"];
arr.sort(function(a, b) {
    return a.localeCompare(b);
});
console.log(arr); // [ "apples", "bananas", "cranberries" ]