Difference between Uint8Array and Uint8ClampedArray

javascript arrays memory-management clamp
Luka picture Luka · Feb 17, 2014 · Viewed 14.3k times · Source

What is the difference between Uint8Array and Uint8ClampedArray in JavaScript? I understand that Uint8ClampedArray is used with canvas for pixel manipulations. Why is that and what is the benefit?

Answer

Felix Kling picture Felix Kling · Feb 17, 2014

Looking at the examples for Uint8ClampedArray and Uint8Array, it looks like the difference is how values are treated when assigned.

If you are trying to set one element to a clamped array to any value outside of the range 0-255, it will simply default to 0 or 255 (depending on whether the value is smaller or larger). A normal Uint8Array array just takes the first 8 bit of the value.

Examples:

var x = new Uint8ClampedArray([17, -45.3]);
console.log(x[0]); // 17
console.log(x[1]); // 0
console.log(x.length); // 2

var x = new Uint8Array([17, -45.3]);
console.log(x[0]); // 17
console.log(x[1]); // 211
console.log(x.length); // 2

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