Logical Expressions Not Obvious

The purpose of this page is to examine how various items are treated when used as booleans.

1. ECMAScript 6 drafts and release candidates
2. ECMAScript standard 5.1

When testing logical operations and methods on some of the values below, the results are not always obvious. (Itested the code below with Safari on Mac OS X. However, you can use whatever browser you like.)

• [] is the shortcut notion for an empty array. If you state that var a = []; the following expressions are true: Boolean(a), a == false, and a != true. The same results occur when the value is created as var a = new Array();
• If you create a new object using var a = {}' or var a = new Object();, the expressions that are true are Boolean(a), a != false, and a != true.
• If you have a string primitive that contains a single blank (e.g., var a = " ";, the following expressions are true: Boolean(a), a == false, and a != true.

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