Question

While debugging javascript written by someone else, I came across some code that I’ve not seen before. Here’s a sample:

function doSomething() {
    //doing something here...
}

function doItNow() {
    //other logic...
    doSomething && doSomething();    // <=== What's this?
}

Is the purpose of the 2nd line in function doItNow() to check if doSomething exists and then call it? Like so:

function doItNow() {
    //other logic...
    if (doSomething) {
        doSomething();
    }
}

JSLint does not like it and I’d rather not have bad code in my app. Any insights?

Answer 1

It’s a ‘shorthand’ indeed. The right side is only executed when the left side passes as if() statement.

Google Closure Compiler and other minifiers take advantage of this; if your input is if(a) a(), it will result in a&&a()

---

You could do the same with ||, for example:

if( !a ){
  alert('Not a');
}

can be written as

a || alert('Not a');