JavaScript/array.html at master · vishal-vaish/JavaScript · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

</body>
</html>
<script>
    const arr=[1,2,3,4,5,6,7];
    //we have square every element of the array
    //.map is used to perform the operation to each element of the array
    const squareArray=arr.map(function(element,index){
        //first argument is the element that you are traversing upon
        //second argument is the index of the element you are transversing in
        // you have necessary to return the result
        return element*element;
    })
    console.log("Two array are",arr,squareArray);

//return all even number from the array
// for this we use filter
const evenArray=arr.filter(function(element,index){
return element%2==0;//here element is checked
})
console.log("Even array is:",evenArray);
//map is used when the new aray is of same length of its parent
//filter is used when the new array is of different length of its parent

// const arr1=[1,2,3,4,5,6,7,8,9,10];
// const tenNumber=arr1.filter(function(element,index){
//     return index<5;
// })
// console.log(tenNumber)
// const arraymultiply=tenNumber.map(function(element,index){
//     return 2*element;
// })
// console.log("2 multiply array is:",arraymultiply);


//reduce return the single element out of all the array elements
const sum=arr.reduce(function(accumulator,currentValue) {
    return accumulator+currentValue;
},0)
console.log("Sum of the array:",sum);

//Array of object
const arrayOfObject=[
{    name:"vishal",
    assignments:4,
},{
    name:"achal",
    assignments:2,
},{
    name:"anshika",
    assignments:3,
}]
//find the object in the array where Name is vishal
//Filter tries to find all the entries that match the criteria
//Find return the first entry that matches the criteria
const name=arrayOfObject.find(function(currentObject){
    return currentObject.name==="vishal"
})
console.log("Name to find",name)

//findIndex return the index
// if no index is found than in findIndex it will return -1 and in find it will return the undefiend
const name1=arrayOfObject.findIndex(function(currentObject){
    return currentObject.name==="vishal"
})
console.log("Name Index",name1)

//traversal of an object
for(let property in arrayOfObject) {
    console.log("Current Property is:",property);
    //how to access values of object
    //if the key name is variable
    console.log("current values",arrayOfObject[property]);
}

for(let element of arr){
    console.log("Current element is", element);
}

//for in works for Object
//for of works for Arrays

arr.forEach(function(currentElement){
    console.log("current for each element is",currentElement);
})
console.log("After array is",arr);
//for each makes changes to the actual array but map does not
//for each does not allow you to return anything
//for each is used for iteration


</script>