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lines changed Original file line number Diff line number Diff line change 1+ filter
2+ // does return a new array
3+ // can manipulate the size of new array
4+ // returns based on condition
5+
6+ const people = [
7+ { name : 'bob' , age : 20 , position : 'developer' } ,
8+ { name : 'peter' , age : 25 , position : 'designer' } ,
9+ { name : 'susy' , age : 30 , position : 'the boss' } ,
10+ { name : 'anna' , age : 35 , position : 'the boss' } ,
11+ ] ;
12+
13+ const youngPeople = people . filter ( function ( person ) {
14+ return person . age <= 25 ;
15+ } ) ;
16+
17+ const developers = people . filter ( function ( person ) {
18+ return person . position === 'senior developer' ;
19+ } ) ;
20+
21+ console . log ( developers ) ;
Original file line number Diff line number Diff line change 1+ // forEach
2+ // does not return new array
3+
4+ const people = [
5+ { name : 'bob' , age : 20 , position : 'developer' } ,
6+ { name : 'peter' , age : 25 , position : 'designer' } ,
7+ { name : 'susy' , age : 30 , position : 'the boss' } ,
8+ ] ;
9+
10+ function showPerson ( person ) {
11+ console . log ( person . position . toUpperCase ( ) ) ;
12+ }
13+
14+ // people.forEach(showPerson);
15+
16+ people . forEach ( function ( item ) {
17+ console . log ( item . position . toUpperCase ( ) ) ;
18+ } ) ;
Original file line number Diff line number Diff line change 1+ // map
2+ // does return a new array
3+ // does not change size of original array
4+ // uses values from original array when making new one
5+
6+ const people = [
7+ { name : 'bob' , age : 20 , position : 'developer' } ,
8+ { name : 'peter' , age : 25 , position : 'designer' } ,
9+ { name : 'susy' , age : 30 , position : 'the boss' } ,
10+ { name : 'anna' , age : 35 , position : 'the boss' } ,
11+ ] ;
12+
13+ const ages = people . map ( function ( person ) {
14+ return person . age + 20 ;
15+ } ) ;
16+ const newPeople = people . map ( function ( person ) {
17+ return {
18+ firstName : person . name . toUpperCase ( ) ,
19+ oldAge : person . age + 20 ,
20+ } ;
21+ } ) ;
22+
23+ const names = people . map ( function ( person ) {
24+ return `<h1>${ person . name } </h1>` ;
25+ } ) ;
26+
27+ document . body . innerHTML = names . join ( '' ) ;
28+
29+ console . log ( names ) ;
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