Script SpringsISSUE #8 of 29

numbers · int · float · NaN · infinity

SparkyVSNaN the Trickster

Sparky saysJS has one number type (64-bit float) covering ints and decimals — plus NaN and Infinity.

There's no separate int type; all numbers are IEEE-754 doubles. That means 0.1 + 0.2 !== 0.3 (floating-point rounding) and integers are exact only up to Number.MAX_SAFE_INTEGER. NaN ("not a number") results from invalid math, and Infinity from overflow or divide-by-zero.

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One number type: 64-bit float (no separate int)
0.1 + 0.2 ≠ 0.3 (floating-point rounding)
NaN = invalid math result
Safe integers up to Number.MAX_SAFE_INTEGER

NaN the Trickster attacks — common mistakes

Comparing floats with === (use a tolerance)
Assuming huge integers stay exact
Treating NaN as comparable (NaN !== NaN)

Boss battleShow that 0.1 + 0.2 is not exactly 0.3, then round it with toFixed.

Example code

<!doctype html><html><head><meta charset="utf-8"></head>
<body style="background:#06040d;color:#e6e0ff;font-family:monospace;padding:20px"><pre id="o"></pre>
<script>const a=0.1+0.2;
document.getElementById('o').textContent='0.1+0.2 = '+a+'\nrounded = '+a.toFixed(2);</script></body></html>

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‹ Data Types · Primitives Vs Objects Number Methods · ToFixed · ParseInt · IsFinite ›