Javascript: What is additional Zero in the if syntax?
javascript
Solution
The `void` operator is very interesting: It accepts an operand, evaluates it, and then the result of the expression is `undefined`. So the `0` isn't extraneous, because the `void` operator requires an operand.
People use `void 0` sometimes to avoid the fact that the `undefined` symbol can be overridden (if you're not using strict mode). E.g.:
undefined = 42;
Separately, the `undefined` in one window is not `===` the `undefined` in another window.
So if you're writing a library and want to be a bit paranoid, either about people redefining `undefined` or that your code may be used in a multi-window situation (frames and such), you might not use the symbol `undefined` to check if something is `undefined`. The usual answer there is to use `typeof whatever === "undefined"`, but `=== void 0` works (well, it may not work in the multi-window situation, depending on what you're comparing it to) and is shorter. :-)
Problem
I have been reading the javascript source of my company project and came across this ``` if (options.parse === void 0) options.parse = true; ``` Not sure what `0` does here?