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I had another question in SO about setTimeout(), where a user mentioned that if the function argument is a string it gets evaluated in global scope, other wise it's not. This was an eye-opener, so I tried to find more info about how setTimeout actually works, but it's not part of the EcmaScript spec and not even MDN had that specific of of information I found in SO.
Is there some good reference about how setTimeout() works?
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This is due to when a function is executed as a parameter to setTimeout , the execution context is different to the execution context of the function! Now this will print out undefined because the this keyword is executed in the context of the setTimeout function and is therefore not defined.
setTimeout() The global setTimeout() method sets a timer which executes a function or specified piece of code once the timer expires.
The setInterval method has the same syntax as setTimeout : let timerId = setInterval(func|code, [delay], [arg1], [arg2], ...) All arguments have the same meaning. But unlike setTimeout it runs the function not only once, but regularly after the given interval of time.
1 Answer. To explain: If you call setTimeout() with a time of 0 ms, the function you specify is not invoked right away. Instead, it is placed on a queue to be invoked “as soon as possible” after any currently pending event handlers finish running.
setTimeout and such aren't in the ECMAScript specification because they're not JavaScript features. They're features of the browser environment's window object. Other environments (Windows Scripting Host, NodeJS, etc.) won't necessarily have those features.
The W3C has been trying to standardize the window object and its various features (including setTimeout), the latest is in the timers section of the HTML5 spec. A lot of it is codifying what browsers already do, although some of it (like saying that the minimum interval value must be 4 [milliseconds]) seems (to me) to be out-of-place for an API specification and implementations seem to make up their own minds (in tests, you can see current browsers happily doing a shorter interval, with the apparent exception of Opera which appears to do what the spec says).
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