At what point does JavaScript determine the left-hand side of an assignment — is it before or after the right-hand side is evaluated?  For example, what does this code do?  var arr = [{thing:1},{thing:2},{thing:3},{last:true}]; arr[arr.length - 1]...

a = 1; b = "1"; if (a == b && a = 1) {     console.log("a==b"); }   The Javascript code above will result in an error in the if statement in Google Chrome 26.0.1410.43:      Uncaught ReferenceError: Invalid left-hand side in a...

I understand that the assignment operator is right associative.  So for example  x = y = z = 2 is equivalent to (x = (y = (z = 2)))  That being the case, I tried the following:  foo.x = foo = {a:1}   I expected that the object foo would be created wi...

In JavaScript, how is the following statement to be interpreted:  cond1 && !await f()   This is an excerpt from the line  if(cond1 && !await f()){     do_stuff(); }   inside a production application. chrome seems to be fine with it, b...

I'm having trouble understanding the order in which an || is executed in Jquery/Javascript.  If I have this:    someVar = $el.attr("one") || options.two || "three";   it sets someVar to "three" when both $el.attr("one&...

var foo = {n: 1}; var bar = foo; foo.x = foo = {n: 2};   what is output for foo.x. My thought is evaluation from right to left so it is equal to   foo = {n:2}; foo.x = foo   so it will be   {     n: 1     x: {n: 2} }   But it is not, it is undefined?...

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var url = age > 18 ? (     alert("OK, you can go."),     // alert returns "undefined", but it will be ignored because     // isn't the last comma-separated value of the parenthesis     "continue.html" // the value to be...

I am now sitting multiple hours in front of a problem that seems rather simple to solve but i just cant get behind it :/  I am defining a small javascript-like language in jison. The problem is that the Parameter rule and the AssignStatement rule bot...

I'm stuck with the following:  foo = properties[field] || overrides.default || config.widget.default || undefined;   with  console.log(properties[field])     // undefined console.log(overrides.default)     // 0 console.log(config.widget.default)...