Uint8ClampedArray() constructor

The Uint8ClampedArray() constructor creates a typed array of 8-bit unsigned integers clamped to 0-255; if you specified a value that is out of the range of [0,255], 0 or 255 will be set instead; if you specify a non-integer, the nearest integer will be set. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).


new Uint8ClampedArray(); // new in ES2017
new Uint8ClampedArray(length);
new Uint8ClampedArray(typedArray);
new Uint8ClampedArray(object);

new Uint8ClampedArray(buffer);
new Uint8ClampedArray(buffer, byteOffset);
new Uint8ClampedArray(buffer, byteOffset, length);



When called with a length argument, an internal array buffer is created in memory, of size length multiplied by BYTES_PER_ELEMENT bytes, containing zeros.


When called with a typedArray argument, which can be an object of any of the typed array types (such as Int32Array), the typedArray gets copied into a new typed array. Each value in typedArray is converted to the corresponding type of the constructor before being copied into the new array. The length of the new typed array will be same as the length of the typedArray argument.


When called with an object argument, a new typed array is created as if by the TypedArray.from() method.

buffer, byteOffset, length

When called with a buffer, and optionally a byteOffset and a length argument, a new typed array view is created that views the specified ArrayBuffer. The byteOffset and length parameters specify the memory range that will be exposed by the typed array view. If both are omitted, all of buffer is viewed; if only length is omitted, the remainder of buffer is viewed.


Different ways to create a Uint8ClampedArray

// From a length
var uintc8 = new Uint8ClampedArray(2);
uintc8[0] = 42;
uintc8[1] = 1337;
console.log(uintc8[0]); // 42
console.log(uintc8[1]); // 255 (clamped)
console.log(uintc8.length); // 2
console.log(uintc8.BYTES_PER_ELEMENT); // 1

// From an array
var arr = new Uint8ClampedArray([21,31]);
console.log(arr[1]); // 31

// From another TypedArray
var x = new Uint8ClampedArray([21, 31]);
var y = new Uint8ClampedArray(x);
console.log(y[0]); // 21

// From an ArrayBuffer
var buffer = new ArrayBuffer(8);
var z = new Uint8ClampedArray(buffer, 1, 4);

// From an iterable
var iterable = function*(){ yield* [1,2,3]; }();
var uintc8 = new Uint8ClampedArray(iterable);
// Uint8ClampedArray[1, 2, 3]


ECMAScript Language Specification (ECMAScript)
# sec-typedarray-constructors

Browser compatibility

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Compatibility notes

Starting with ECMAScript 2015, Uint8ClampedArray constructors require to be constructed with a new operator. Calling a Uint8ClampedArray constructor as a function without new, will throw a TypeError from now on.

var dv = Uint8ClampedArray([1, 2, 3]);
// TypeError: calling a builtin Uint8ClampedArray constructor
// without new is forbidden
var dv = new Uint8ClampedArray([1, 2, 3]);

See also