array.html

<script>

    //1. array mutation -> there are some function array function which mutate the original array when we use tham.

    const arr = [1,2,3,4,5,6,7,8,9,];

    const rev = arr.reverse();
    // here we used the reverse function which is a mutation function that means it will change the original array as well.
    // the arr also will be reversed even if we use rev variable.
    // that is called the mutation function.
    console.log(rev);

    // immutable function. -> they do not change the original data.

    const arr2 = [1,2,3,4,5,6,7,8,9,];

    const slice = arr2.slice(3,6);

    console.log(slice);

    // now what if you want to use mutation fun and do not want to change the original array.
    // we use ... operator.

    const arr3 = [1,2,3,4,5,6,7,8,9,];

    const rev3 = [...arr3].reverse();

    console.log(rev3);

    // the two fun which always confuse you.
    // they both used to get a subset of an array.
    // slice -> it is immutable.
    // splice. -> it is mutable.

    const arr4 = [1,2,3,4,5,6,7,8,9,];
    console.log('before -> ', arr4);
    const arr5 = arr4.splice(2,5);
    console.log('after -> ', arr4);
    console.log(arr5);

    // add an item to middle of the array.
    // no fun here to add item in the middle.
    // so do like this.

    const arr6 = [1,2,3,5,6,7,8,9,]

    const arr7 = [
        ...arr6.slice(0,3),
        4,
        ...arr6.slice(3)
    ];

    console.log(arr7);

    // delete the item.

    const arr8 = [1,2,3,4,5,6,7,8,9,];

    const arr9 = [
        ...arr8.slice(0,3),
        ...arr8.slice(4)
    ];
    console.log(arr9);

    // delete using find index .

    const arr10 = [
        {
            name: 'srk',
            age : 24
        },
        {
            name: 'hardik',
            age : 25
        },
        {
            name: 'abc',
            age : 242
        },
        {
            name: 'navdeep',
            age : 22
        }
    ];
    // 1.
    const index = arr10.findIndex(value => {
        if(value.name === 'abc'){
            return true;
        }
        return;
    });
    // 2.
    const index2 = arr10.findIndex(value => value.name === 'abc' );

    const arr11 = [
        ...arr10.slice(0,index),
        ...arr10.slice(index + 1)
    ]

    console.log(arr11);

    // some array fun.

    // create an array given values.
    console.log(Array.of('srk', 'hardik'));

    //this fun will create an array up to 10 and set value srk.
    const arr12 = Array.from({length: 10}, () => {
        return 'srk';
    });

    console.log(arr12);

    // Array.isArray -> will check whether we have array or not.

    console.log(typeof arr); // -> will give object.
    console.log(Array.isArray(arr)) // -> will give true.

    //join will join the array.
    const joinarr = arr.join("");
    console.log(joinarr);

    // split will split the value and turn it into an array on the basis of argument given..
    const str = "srk, hardik, navdeep";
    console.log(str.split(","));
    console.log(joinarr.split(""));


</script>