I don't understand function return in javascript

Question

Can anyone explain why javascript return statement is used in function? when and why we should use it?

Please help me.

Answer 1

You use a return statement for two reasons:

1. To return a specific value from a function.

2. To finish the execution of the function before the last line of code in the function.

Without any return value; statement, the function does not return a specific value (technically the return value is undefined).

Without a specific return statement somewhere in the function, the function runs until the last line of code in the function.

Examples:

function add(x, y) {
    // return a sum of the two arguments
    return x + y;
}

console.log(add(1, 3));    // 4


function findParm(str, key) {
    if (!str || !key) {
         // invalid parameters, so return null
         return null;
    }
    var pieces = str.split("&");
    for (var i = 0; i < pieces.length; i++) {
        var loc = str.indexOf(pieces[i] + "=");
        if (loc >= 0) {
            // when we've found a match, return it and finish execution of the function
            return str.slice(loc + key.length + 1);
        }
    }
    // no match found, return null
    return null;
}

var str = "user=John&login=yes"
findParam(str, "login");          // "yes"