Type explorer

How to use it

1. Operator: pick a left value, an operator (==, ===, +, -, &&, || or ??) and a right value. Read the result and its type, then the steps, each named for the part of the ECMAScript specification it comes from. Predict the result first, then check.
2. == matrix: == for every pair of the same values. The grid scrolls inside its own box. Choose a cell to open that pair in operator mode. With a keyboard, tab into the grid, move with the arrow keys, and press Enter.
3. One value: pick a value and read typeof, Number(), String() and Boolean(), with the reason for each.

The values come from a fixed list of the awkward ones. Nothing you type is run. A pair is two separate literals, so [] against [] compares two different arrays. The results come from the real operators, in type-explorer.js, and a test checks every stated result and conversion against JavaScript for every pair.

Learn more

• Types and coercion: the conversion tables, + against the other operators, == against ===, and NaN.
• The JavaScript section.
• The specification's IsLooselyEqual and ApplyStringOrNumericBinaryOperator, the algorithms the steps follow.