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Slice
Syntax
arrName.slice();
arrName.slice(start);
arrName.slice(start, end);
Description
The slice() method returns a copy of the array. It takes two optional parameters, the start of the slice and the end of the slice.
If no parameters are passed to slice(), a copy of the array is returned.
If one parameter, start, is passed to slice(), a copy of the string from start (inclusive) to the end of the string is returned.
If two parameters are passed to slice(), start and end, a copy of the string from start (inclusive) to end (exclusive) is returned.
Examples
var arr = ['a', 'b', 'c', 'd'];
var copy = arr.slice(); // ['a', 'b', 'c', 'd']
var sliced = arr.slice(0, 2); // [a, b]
Splice
Syntax
arrName.splice(start);
arrName.splice(start, deleteCount);
arrName.splice(start, deleteCount, elementToAdd1, elementToAdd2, ...elementToAddN);
Description
The splice() method adds or removes elements from an array and returns an array containing the deleted elements.
It takes an infinite number of parameters.
The first parameter, start, is the index where the splice begins.
The second parameter, deleteCount, refers to the number of elements to delete.
The next parameters, elementToAdd1 through elementToAddN, adds those elements at index start.
Examples
var myFish = ['angel', 'clown', 'mandarin', 'sturgeon'];
myFish.splice(2, 0, 'drum', 'tuba'); // insert 'drum' at 2-index position
// myFish is ["angel", "clown", "drum", "tuba", "mandarin", "sturgeon"]
myFish.splice(2, 1); // remove 1 item at 2-index position (that is, "drum")
// myFish is ["angel", "clown", "mandarin", "sturgeon"]
Push
Syntax
// all return length of arrName
arrName.push();
arrName.push(elementToAdd1, ..., elementToAddN);
Description
The push() method adds one or more elements to the end of an array and returns the new length of the array.
It takes an infinite number of optional parameters, the elements to add.
Examples
var numbers = [1, 2, 3];
numbers.push(4);
console.log(numbers); // [1, 2, 3, 4]
numbers.push(5, 6, 7);
console.log(numbers); // [1, 2, 3, 4, 5, 6, 7]
Unshift
Syntax
// all return length of arrName
arrName.unshift();
arrName.unshift(elementToAdd1, ..., elementToAddX);
Description
The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.
Examples
var a = [1, 2, 3];
a.unshift(4, 5);
console.log(a); // [4, 5, 1, 2, 3]
Pop
Syntax
arrName.pop();
Description
The pop() method removes the last element from an array and returns that element. This method changes the length of the array.
Examples
var a = [1, 2, 3];
a.pop(); // 3
console.log(a); // [1, 2]
Shift
Syntax
arrName.shift();
Description
The shift() method removes the first element from an array and returns that element. This method changes the length of the array.
Examples
var a = [1, 2, 3];
var b = a.shift();
console.log(a); // [2, 3]
console.log(b); // 1
Concat
Syntax
arrToAddTo1.concat(arrToAdd1, arrToAdd2, ..., arrToAddN);
Description
The concat() method is used to merge two or more arrays. This method does not change the existing arrays but instead returns a new array.
Examples
var arr1 = ['a', 'b', 'c'];
var arr2 = ['d', 'e', 'f'];
var arr3 = arr1.concat(arr2); // [ "a", "b", "c", "d", "e", "f" ]
Join
Syntax
arrName.join(); // if no parameter used, a comma (,) is used as glue
arrName.join(glue);
Description
The join() method takes in one optional string parameter, glue, which is used to join all elements of an array into a string.
Examples
var a = ['Wind', 'Rain', 'Fire'];
a.join(); // 'Wind,Rain,Fire'
a.join('-'); // 'Wind-Rain-Fire'
IndexOf
Syntax
arrName.indexOf(needle);
arrName.indexOf(needle, indexFrom);
Description
The indexOf() method returns the first index at which a given element can be found in the array or -1 if it is not present.
The first parameter, needle, is the element to search for.
The second parameter, indexFrom, is the index of the array to search from.
Examples
var a = [2, 9, 9];
a.indexOf(2); // 0
a.indexOf(7); // -1
if (a.indexOf(7) === -1) {
// element doesn't exist in array
}
How can we test if an element DOES exist in the array?