array utilities

utils.js

// Using slice() to Remove value from beginning and end of string.
sliceString = function (value) {
    let result = value.slice(1, -1);
    return result;
}


// Using splice() method to changes the contents of an array by removing 
// or replacing existing elements and/or adding new elements
var months = ['Jan', 'March', 'April', 'June'];

spliceGene = function (array) {
    let result = array.splice(1, 3, 'Feb');
    return result;
}

// unshift: Adds item to front of array
unshift = function () {
    var fruits = ["Banana", "Orange", "Apple", "Mango"];
    fruits.unshift("Lemon", "Pineapple");
    console.log(fruits)
}

shift = function () {
    var fruits = ["Banana", "Orange", "Apple", "Mango"];
    var x = fruits.shift();
    console.log(x);
}

// We can use the shift() method in while loop like this.
shift2 = function () {
    let names = ["Harvey", "Donna", "Mike", "Rachel", "Louis", "Jessica"];
    while ((i = names.shift()) !== undefined) {
        console.log(i);
    }
}

// Ways to Remove Elements From A JavaScript Array
var ar = [1, 2, 3, 4, 5, 6];
ar.pop(); // returns 6
console.log(ar); // [1, 2, 3, 4, 5]

var ar = ['zero', 'one', 'two', 'three'];
ar.shift(); // returns "zero"
console.log(ar); // ["one", "two", "three"]

var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
var removed = arr.splice(2, 2); // removed === [3, 4]

["bar", "baz", "foo", "qux"]
list.splice(0, 2)
// Starting at index position 0, remove two elements ["bar", "baz"] and retains ["foo", "qux"]


// /Removing Array Items By Value Using Splice
var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
for (var i = 0; i < arr.length; i++) {
    if (arr[i] === 5) {
        arr.splice(i, 1);
    }
}

var arr = [1, 2, 3, 4, 5, 5, 6, 7, 8, 5, 9, 0];
for (var i = 0; i < arr.length; i++) {
    if (arr[i] === 5) {
        arr.splice(i, 1);
        i--;
    }
}


// Using the Array filter Method to Remove Items By Value
var array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
var filtered = array.filter(function (value, index, arr) {
    return value > 5;
});


// Making a Remove Method
function arrayRemove(arr, value) {
    return arr.filter(function (ele) {
        return ele != value;
    });

}
var result = arrayRemove(array, 6);
// result = [1, 2, 3, 4, 5, 7, 8, 9, 0]


// Explicitly Remove Array Elements Using the Delete Operator
var ar = [1, 2, 3, 4, 5, 6];
delete ar[4]; // delete element with index 4
console.log(ar); // [1, 2, 3, 4, undefined, 6]
alert(ar); // 1,2,3,4,,6


// Clear or Reset a JavaScript Array
var ar = [1, 2, 3, 4, 5, 6];
ar = [];

var ar = [1, 2, 3, 4, 5, 6];

console.log(ar); // Output [1, 2, 3, 4, 5, 6]

ar.length = 0;

console.log(ar); // Output []



var ar = [1, 2, 3, 4, 5, 6];

console.log(ar); // Output [1, 2, 3, 4, 5, 6]

ar.splice(0, ar.length);



console.log(ar); // Output []

var ar = [1, 2, 3, 4, 5, 6];

console.log(ar); // Output [1, 2, 3, 4, 5, 6]



while (ar.length) {
    ar.pop();
}

console.log(ar); // Output []