Flow control lets you run a block of code under certain conditions. You should always use braces to mark the start and end of logical blocks.[1]
Example 8.12. Flow control
var foo = true; var bar = false; if (foo) { console.log('hello!'); } if (bar) { // this code won't run } else if (foo) { // this code will run } else { // this code would run if foo and bar were both false }
In order to
Example 8.13. Values that evaluate to true
'0'; 'any string'; []; // an empty array {}; // an empty object 1; // any non-zero number
Example 8.14. Values that evaluate to false
0; ''; // an empty string NaN; // JavaScript's "not-a-number" variable null; undefined; // be careful -- undefined can be redefined!
[1] Strictly speaking, braces aren't required around single-line if statements, but using them consistently, even when they aren't strictly required, makes for vastly more readable code.