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// The copyWithin() method shallow copies part of an array to another location in the same array and returns it without modifying its length.

// ----Native Syntax----
// arr.copyWithin(target[, start[, end]])

// ----Parameters----
// ARRAY
// TARGET
	// the index at which to copy the sequence to
// START
	// the index to begin copying
	// defaults to index 0
// END
	// the index copied up to but not including
	// defaults to array.length

// ----Return Value----
// the modified array

// ----Requirements----
// it should return the same array, not a new one

// it should copy the sequence to target index
// it should begin copying at start
// it should copy upto but not including end

// it should treat target as an offset from the end of the array if it is a negative number
// it should treat start as an offset from the end of the array if it is a negative number
// it should treat end as an offset from the end of the array if it is a negative number

// it should round target down to the nearest integer if it has a decimal value
// it should round start down to the nearest integer if it has a decimal value
// it should round end down to the nearest integer if it has a decimal value

// it should round target up to the nearest integer if it has a negative decimal value
// it should round start up to the nearest integer if it has a negative decimal value
// it should round end up to the nearest integer if it has a negative decimal value

// it should accept objects resembling arrays

// it should not alter the length property of the object passed through

// what if length is a decimal
// what if no length
// what if length is negative
// what if you pass in a string, a boolean, a number


function copyWithin(array, target, start, end) {
	if (this) {
		array = this;
		if (typeof array === 'object') {
			[].unshift.call(arguments, array);
		}
	}
	if (typeof array !== 'object') {
		// convert array to object
	 	array = {}.valueOf.call(array);
	}

	if (!start) {
		arguments[2] = 0;
	}
	if (!end) {
		arguments[3] = array.length;
	}
	for (let i = 1; i < 4; i++) {
		if (Number.isInteger(arguments[i]) === false) {
			arguments[i] = arguments[i] | 0;
		}
		if (arguments[i] < 0) {
			arguments[i] = array.length + arguments[i];
		}
	}
	target = arguments[1];
	start = arguments[2];
	end = arguments[3];

	let length = array.length
	if (Number.isInteger(array.length) === false) {
		length = Math.floor(length);
	}
	let originalArray = JSON.parse(JSON.stringify(array));

	for (let j = start; j < end; j++) {
		if (target === length) {
			return array;
		}
		array[target] = originalArray[j];
		target++;
	}

	return array;
};

tests({
	'1. it should return the same array, not a new one': function() {
		let array = ['I should be the array that gets returned']
		let sameArray = copyWithin(array);
		eq(sameArray, array);
	},

	'2. it should copy the sequence to target index': function() {
		let array = [1, 2, 3]
		copyWithin(array, 1, 0, 2);
		eq(array[1], 1);
	},
	'3. it should begin copying at start': function() {
		let array = [1, 2, 3]
		copyWithin(array, 0, 1, 2);
		eq(array[0], 2);
	},
	'4. it should copy upto but not including end': function() {
		let array = [1, 2, 3]
		copyWithin(array, 0, 1, 2);
		eq(array[0], 2);
		eq(array[1], 2);
		eq(array[2], 3);
	},

	'5. it should default start to 0': function() {
		let array = [1, 2, 3]
		copyWithin(array, 2);
		eq(array[2], 1);
	},
	'6. it should default end to array.length': function() {
		let array = [1, 2, 3]
		copyWithin(array, 0);
		eq(array[2], 3);
	},

	'7. it should copy the elements original value if an element is overwritten before being reached': function() {
		let array = [1, 2, 3, 4, 5];
		copyWithin(array, 2);
		eq(array[4], 3);
	},
	'8. it should not alter the length of the array': function() {
		let array = [1, 2, 3];
		copyWithin(array, 2);
		eq(array.length, 3);
	},

	'9. it should treat target as an offset from .length if it is a negative number': function() {
		let array = [1, 2, 3];
		copyWithin(array, -1);
		eq(array[array.length - 1], 1);
	},
	'10. it should treat start as an offset from the end of the array if it is a negative number':function() {
		let array = [1, 2, 3];
		copyWithin(array, 0, -1);
		eq(array[0], 3);
	},
	'11. it should treat end as an offset from the end of the array if it is a negative number': function() {
		let array = [1, 2, 3, 4, 5];
		copyWithin(array, 0, 1, -3);
		eq(array[0], 2);
		eq(array[1], 2);
	},

	'12. it should round target down to the nearest integer if it has a decimal value': function() {
		let array = [1, 2, 3];
		copyWithin(array, 1.8);
		eq(array[1], 1);
	},
	'13. it should round start down to the nearest integer if it has a decimal value': function() {
		let array = [1, 2, 3];
		copyWithin(array, 0, 1.8);
		eq(array[0], 2);
	},
	'14. it should round end down to the nearest integer if it has a decimal value': function() {
		let array = [1, 2, 3, 4];
		copyWithin(array, 0, 1, 3.8);
		eq(array[1], 3);
		eq(array[2], 3);
	},

	'15. it should round target up to the nearest integer if it has a negative decimal value': function() {
		let array = [1, 2, 3];
		copyWithin(array, -1.8);
		eq(array[2], 1);
	},
	'16. it should round start up to the nearest integer if it has a negative decimal value': function() {
		let array = [1, 2, 3];
		copyWithin(array, 0, -1.8);
		eq(array[0], 3);
	},
	'17. it should round end up to the nearest integer if it has a negative decimal value': function() {
		let array = [1, 2, 3];
		copyWithin(array, 0, 1, -1.8);
		eq(array[0], 2);
		eq(array[1], 2);
	},

	'18. it should accept objects resembling arrays': function() {
		let obj = {0:0, 1:1, 2:2, length: 3};
		copyWithin(obj, 1 );
		eq(obj[1], 0);
		eq(obj[2], 1);
	},
	'19. it should treat length as the closest whole number < length, if length is a negative number': function() {
		let obj = {0:0, 1:1, 2:2, length: 2.8};
		copyWithin(obj, 0, 1);
		eq(JSON.stringify(obj), JSON.stringify({ 0:1, 1:1, 2:2, length: 2.8 }));
	},
	'20. it should do nothing of significance if length is 0, < 0, or NaN': function() {
		let obj = {0:0, 1:1, 2:2, length: 'string'};
		copyWithin(obj, 0, 1);
		eq(JSON.stringify(obj), JSON.stringify({0:0, 1:1, 2:2, length: 'string'}));

		obj = {0:0, 1:1, 2:2, length: -2};
		copyWithin(obj, 0, 1);
		eq(JSON.stringify(obj), JSON.stringify({0:0, 1:1, 2:2, length: -2}));

		obj = {0:0, 1:1, 2:2};
		copyWithin(obj, 0, 1);
		eq(JSON.stringify(obj), JSON.stringify({0:0, 1:1, 2:2}));
	},
	'21. it should convert array value to an object if possible': function() {
		eq(typeof (copyWithin.call(true)) === 'object', true);
	},
	'22. it should work with apply': function() {
		let obj = {0:0, 1:1, 2:2, length: 3};
		let arg = [1, 0, 3]
		copyWithin.apply(obj, arg);
		eq(obj[1], 0);
		eq(obj[2], 1);
	},
});



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