Useful Functions
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Map function
will duplicate an array to another
This will retrieve the ages of everyone 18 or over and add them to the array full
var ages[12, 13, 16, 21] var full = ages.map(function(curr){ return cur >=18; })
This will get the 'true' boolean value of ages>= 18 then we have to use the indexOf to find the element position
console.log(ages[full.indexOf(true)]);
ES6 Equivalent This returns the index
var index = ages.findIndex(cur => cur >= 18);
This returns the actual age
var ageover18 = ages.find(cur => 18);
Apply
function addFourAges(a,b,c,d){ return a+b+c+d; }; var sum1 = addFourAges(18,19,20,21);
Each age is passed as a variable to the function, but if the ages were in an array, we can use the apply method to pass them into the function
var ages = [18,21,22,23]; var sum2 = addFourAges.apply(null, ages); // the null refers to the this
ES6 Spread Operator
ES6 Equivalent Spread Operator
const sum3 = addFourAges(...ages); // the ... means the ages array is expanded into individual components.
Join two Arrays
const arrayOne= ['hello', 'two']; const arrayTwo = ['three', 'four']; const arrayThree = [...arrayOne, ...arrayTow];
Looping through all elements and changing the color
const h = document.querySelector(h1) const boxes = documwnt.querySelectorAll('.box');
const all = [h, ...boxes]; Array.form(all).forEach(cur=> cur.style.color='purple') // returns an array
Argument function
Allows you to pass an unlimited number of arguments to a function
function isFullAge(){ var args = Array.prototype.slice.call(arguments); args.forEach(function(cur){ console.log(2016 - cur) >= 18); }) isFullAge(1990,1921,1967);
ES6 Equivalent Rest Parameter
function isFullAge(...years){ console.log(years); } isFullAge(1990,1921,1967);
Splice
indexOf
Split
Used to split text given a delimiter into an array of substrings
var myText = 'hello-1' var mysplit = myText.split('-')
Will Yield
['hello', 1]