JavaScript中的运算符优先级

Question

I am reading operator precedence on this page . It shows "===" has higher precedence than "||" operator. If it is true, then "a === doesThisHappen()" will run first. But why I did not get console.log('This happens!')?

var a;

a = 1;

function doesThisHappen() {

    console.log('This happens!');

    return 0;
}

if (a || a === doesThisHappen()) {
    console.log('Something is there.');
}

Answer 1

Order of evaluation and operator precedence are orthogonal concepts. In a || b a || b the left side a is evaluated first no matter what the right side b contains. More over, if the left side evaluates to true the right side is not evaluated.