JS ES5: filter

1. method
2. creates a new array filled with all array elements that pass a test (provided as a function).
3. does not execute the function for array elements without values.
4. does not change the original array.

 

[Syntax]

let newArray = arr.filter(callback(element[, index, [array]])[, thisArg])

▽

callback	Required	A function to be run for each element in the array.
		is a predicate, to test each element of the array. Return true to keep the element, false otherwise.
		function(element, index, array)	element Required The value of the current element being processed in the array.
			index Optional The array index of the current element being processed in the array.
			array Optional.  The array object the current element belongs to. The array filter was called upon. : why need this argument...?
thisArg	Optional	A value to be passed to the function to use as its "this" value when executing callback.
		If this parameter is empty, the value "undefined" will be passed as its "this" value

 

[Return value]

   : A new array containing all the array elements that pass the test.
   : If no elements pass the test, an empty array will be returned.

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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter

https://www.w3schools.com/jsref/jsref_filter.asp