Posted in Interesting, Programming, Web Tech

Fun with JS array functions

If you are a JS programmer you must have used arrays quite often. While working with arrays, we somehow always tend to use for loop or Array.forEach() function followed by conditional if-else block checking. To bring into practice the use of already existing prototype array functions we have to understand when to use which functions. So, lets have some fun in understanding and KISS(Keep It Simple, Stupid!). Most of this function are self explanatory from their names itself.

Array.find() method returns the value of first element present in the array that satisfies the testing condition else returns undefined.
var arr = [35, 98, 78, 1, 8, 3];
var findEle = arr.find(function(ele){
return ele > 50;
});
console.log(findEle);

This will return 98 which is the first element that satisfies condition ele > 50.

Array.findIndex() method returns the index of the first element in the array that satisfies the provided testing function else returns -1.
var arr = [35, 98, 78, 1, 8, 3];
var findEleIndex = arr.findIndex(function(ele){
return ele < 10;
});
console.log(findEleIndex);

This will return 3 which is the index of first element that satisfies condition ele < 10.

Array.includes()method determines whether an element is present and returns boolean.
var arr = [35, 98, 78, 1, 8, 3];
var isPresent = arr.includes(98);
console.log(isPresent);

This will return true as 98 is present in the array arr.

Array.some() method determines whether atleast one element of the array satisfies the testing condition and returns boolean.
var arr = [35, 98, 78, 1, 8, 3];
var isPresent = arr.some(function(ele){
return ele > 50;
});
console.log(isPresent);

Array.every() method tests whether every array element passes the test and returns boolean.
var arr = [35, 98, 78, 1, 8, 3];
var test = arr.every(function(ele){
ele > 10;
});
console.log(test);

This will return false as 1 and 3 are less than 10 and test condition fails.

Array.map() creates a new array by applying some action on every element in the original array.
var arr = [35, 98, 78, 1, 8, 3];
var mapValue = arr.map(function(ele){
return ele * 2;
});
console.log(mapValue);

This will return an [70, 196, 156, 2, 16, 6].

Array.forEach() executes action(s) for every elemnt in the array. It is similar to for loop.

Array.filter() creates a new array depending on if the condition is satisfied or not.
var arr = [35, 98, 78, 1, 8, 3];
var mapValue = arr.filter(function(ele){
return ele > 50;
});
console.log(ele);

This returns [98, 78].

Author:

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