hugolpz · March 15, 2021 18:39
diff --git a/javascript_array_methods.js b/javascript_array_methods.js
 // DATA : few common array samples to manipulate.
 var letters = ['a', 'b', 'c'],
    numbers = [2, 3, 4, 5, 6, 7, 8],
    members = [
    	{ 'name': 'A', 'group':'Bird', 'rank': 1, 'age': 24},
    	{ 'name': 'B', 'group':'Wolf', 'rank': 3, 'age': 12},
    	{ 'name': 'C', 'group':'Fox',  'rank': 2, 'age':  9},
    	{ 'name': 'D', 'group':'Bird', 'rank': 4, 'age': 27}
    ];
 var bin= [];

 // FOREACH, MAP, REDUCE
 // [].forEach() : process over something
 ['a', 'b', 'c'].forEach(function(item, index, initialArr) {
  // do some processing here.
  if(index===0) console.log('[].forEach(): ', initialArr, item, index, this, this[index]);
 }, [4, 5, 6]);
 ['a', 'b', 'c'].forEach(item => bin.push(item.toUpperCase() ));
 console.log('[].forEach():', bin)  // ['A', 'B', 'C']

 // [].map() : creates new array populated with the results of each element, itself processed by custom function
 var groupsAll = members.map(function(member) { return member.group; });
 var groupsAll = members.map(member => member.group);
 console.log('[].map(): ', groupsAll) // ["Bird", "Wolf", "Fox", "Bird"]

 // [].reduce() : iterate through array and process from initial value by custom operation (sum, multi, etc), resulting in single output value.
 var experience= members.reduce(function(intermediateResult,item) { return intermediateResult + item.age; }, 0)
 var experience= members.reduce( (intermediateResult,item) => intermediateResult+item.age, 0 )
 console.log("[].reduce(): "+ experience) // 72

 // FILTER & FIND
 // [].filter() : creates new array with all elements that pass the condition.
 var passFilter = numbers.filter(function(number) { return number >= 6});
 var passFilter = numbers.filter(number => number >= 6);
 console.log('[].filter(): ',passFilter); // [6,7,8]

 // [].find : returns value of first element matching condition.
 var found = members.find(function(member) { return member.age > 5; });
 var found = members.find(member => (member.age > 5));
 console.log('[].find(): ',found) //{ age: 24, group: "Bird", name: "A", rank: 1 }

 // SOME & EVERY
 // [].some() : check if one or more elements respect condition, returns true or false.
 var majorPresent = members.some(function(member,i,arr){ return member.age >= 18 });
 var major = members.some(member => member.age > 18);
 console.log('[].some(): ', majorPresent) // true

 // [].every() : check if every elements respect condition, returns true or false.
 var majorOnly = members.every(function(member,i,arr){ return member.age >= 18 });
 var major = members.every(x => x.age > 18);
 console.log('[].every(): ', majorOnly) // false

 // SET (Uniques)
 // [] Set : process to create array of values without any duplication
 var namesUniq = [...new Set(members.map(member => member.group))];
 console.log("Uniques: ", namesUniq )

 // SLICE & SPLICE
 // [].slice([start[, end]]) : creates new array with elements from index 'start' to index 'end'
 var kept = numbers.slice(2,5);
 console.log(kept)// [4,5,6]; `numbers` unchanged.

 // [].splice(x,n) : remove from item==x, for n items.
 var numbers2= numbers;
 var deleted = numbers2.splice(2, 3);
 // numbers2 now [1, 2, 6, 7, 8] 
 // deleted is [3, 4, 5]

 // Compare 2 arrays
 let intersection= arrA.filter(x => arrB.includes(x));   // Intersection
 let difference  = arrA.filter(x =>!arrB.includes(x));   // In A only
 let union  = [...new Set([...arrA, ...arrB])];           // Union : uniques
 let unionXl= [...arrA, ...arrB];                         // Union : full list
 // Symetrical difference (Union unique minus intersection):
 let diff = arrA.filter(x => !arrB.includes(x))
    .concat(arrB.filter(x => !arrA.includes(x)));
	// DATA : few common array samples to manipulate.
	var letters = ['a', 'b', 'c'],
	numbers = [2, 3, 4, 5, 6, 7, 8],
	members = [
	{ 'name': 'A', 'group':'Bird', 'rank': 1, 'age': 24},
	{ 'name': 'B', 'group':'Wolf', 'rank': 3, 'age': 12},
	{ 'name': 'C', 'group':'Fox', 'rank': 2, 'age': 9},
	{ 'name': 'D', 'group':'Bird', 'rank': 4, 'age': 27}
	];
	var bin= [];

	// FOREACH, MAP, REDUCE
	// [].forEach() : process over something
	['a', 'b', 'c'].forEach(function(item, index, initialArr) {
	// do some processing here.
	if(index===0) console.log('[].forEach(): ', initialArr, item, index, this, this[index]);
	}, [4, 5, 6]);
	['a', 'b', 'c'].forEach(item => bin.push(item.toUpperCase() ));
	console.log('[].forEach():', bin) // ['A', 'B', 'C']

	// [].map() : creates new array populated with the results of each element, itself processed by custom function
	var groupsAll = members.map(function(member) { return member.group; });
	var groupsAll = members.map(member => member.group);
	console.log('[].map(): ', groupsAll) // ["Bird", "Wolf", "Fox", "Bird"]

	// [].reduce() : iterate through array and process from initial value by custom operation (sum, multi, etc), resulting in single output value.
	var experience= members.reduce(function(intermediateResult,item) { return intermediateResult + item.age; }, 0)
	var experience= members.reduce( (intermediateResult,item) => intermediateResult+item.age, 0 )
	console.log("[].reduce(): "+ experience) // 72

	// FILTER & FIND
	// [].filter() : creates new array with all elements that pass the condition.
	var passFilter = numbers.filter(function(number) { return number >= 6});
	var passFilter = numbers.filter(number => number >= 6);
	console.log('[].filter(): ',passFilter); // [6,7,8]

	// [].find : returns value of first element matching condition.
	var found = members.find(function(member) { return member.age > 5; });
	var found = members.find(member => (member.age > 5));
	console.log('[].find(): ',found) //{ age: 24, group: "Bird", name: "A", rank: 1 }

	// SOME & EVERY
	// [].some() : check if one or more elements respect condition, returns true or false.
	var majorPresent = members.some(function(member,i,arr){ return member.age >= 18 });
	var major = members.some(member => member.age > 18);
	console.log('[].some(): ', majorPresent) // true

	// [].every() : check if every elements respect condition, returns true or false.
	var majorOnly = members.every(function(member,i,arr){ return member.age >= 18 });
	var major = members.every(x => x.age > 18);
	console.log('[].every(): ', majorOnly) // false

	// SET (Uniques)
	// [] Set : process to create array of values without any duplication
	var namesUniq = [...new Set(members.map(member => member.group))];
	console.log("Uniques: ", namesUniq )

	// SLICE & SPLICE
	// [].slice([start[, end]]) : creates new array with elements from index 'start' to index 'end'
	var kept = numbers.slice(2,5);
	console.log(kept)// [4,5,6]; `numbers` unchanged.

	// [].splice(x,n) : remove from item==x, for n items.
	var numbers2= numbers;
	var deleted = numbers2.splice(2, 3);
	// numbers2 now [1, 2, 6, 7, 8]
	// deleted is [3, 4, 5]

	// Compare 2 arrays
	let intersection= arrA.filter(x => arrB.includes(x)); // Intersection
	let difference = arrA.filter(x =>!arrB.includes(x)); // In A only
	let union = [...new Set([...arrA, ...arrB])]; // Union : uniques
	let unionXl= [...arrA, ...arrB]; // Union : full list
	// Symetrical difference (Union unique minus intersection):
	let diff = arrA.filter(x => !arrB.includes(x))
	.concat(arrB.filter(x => !arrA.includes(x)));