var bind = require('../internals/function-bind-context');
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var call = require('../internals/function-call');
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var aConstructor = require('../internals/a-constructor');
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var toObject = require('../internals/to-object');
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var lengthOfArrayLike = require('../internals/length-of-array-like');
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var getIterator = require('../internals/get-iterator');
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var getIteratorMethod = require('../internals/get-iterator-method');
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var isArrayIteratorMethod = require('../internals/is-array-iterator-method');
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var aTypedArrayConstructor = require('../internals/array-buffer-view-core').aTypedArrayConstructor;
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module.exports = function from(source /* , mapfn, thisArg */) {
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var C = aConstructor(this);
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var O = toObject(source);
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var argumentsLength = arguments.length;
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var mapfn = argumentsLength > 1 ? arguments[1] : undefined;
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var mapping = mapfn !== undefined;
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var iteratorMethod = getIteratorMethod(O);
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var i, length, result, step, iterator, next;
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if (iteratorMethod && !isArrayIteratorMethod(iteratorMethod)) {
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iterator = getIterator(O, iteratorMethod);
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next = iterator.next;
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O = [];
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while (!(step = call(next, iterator)).done) {
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O.push(step.value);
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}
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}
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if (mapping && argumentsLength > 2) {
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mapfn = bind(mapfn, arguments[2]);
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}
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length = lengthOfArrayLike(O);
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result = new (aTypedArrayConstructor(C))(length);
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for (i = 0; length > i; i++) {
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result[i] = mapping ? mapfn(O[i], i) : O[i];
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}
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return result;
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};
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