Travase Objects and four method of array
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var iterableObj = {
"lastName":'luo',
"firstName":'xu',
"age":19
}
let keys = Object.keys(iterableObj); //return array of keys in the iterableObj
// console.log(keys) //Array(3) [ "lastName", "firstName", "age" ]
let vals = Object.values(iterableObj);
//console.log(vals) //["luo","xu",19]
let entries = Object.entries(iterableObj)
//console.log(entries) //[["lastName", "luo"],[ "firstName", "xu"],["age", 19]] 2-D arrays
const companies = [ //array
{name: "Company One", category: "Finance", start: 1981, end: 2003}, //object
{name: "Company Two", category: "Retail", start: 1992, end: 2008},
{name: "Company Three", category: "Auto", start: 1999, end: 2007},
{name: "Company Four", category: "Retail", start: 1989, end: 2010},
{name: "Company Five", category: "Technology", start: 2009, end: 2014},
{name: "Company Six", category: "Finance", start: 1987, end: 2010},
{name: "Company Seven", category: "Auto", start: 1986, end: 1996},
{name: "Company Eight", category: "Technology", start: 2011, end: 2016},
{name: "Company Nine", category: "Retail", start: 1981, end: 1989}
];
const ages = [33, 12, 20, 16, 5, 54, 21, 44, 61, 13, 15, 45, 25, 64, 32];
//1. forEach()
for (let i = 0; i < companies.length; i++){
// console.log(companies[1]);
}
companies.forEach(function (company, index , companies) { //we can pass 2 params
// console.log(company);
});
//2. filter()
//store the person'age over 21, who can drink
var canDrink = [];
for (let i=0; i< ages.length ; i++){
if (ages[i] >= 21){
canDrink.push(ages[i]);
}
}
canDrink = ages.filter(function (age) {
if (age >= 21){
return true;
}
});
canDrink = ages.filter(age => age >=21);
console.log(canDrink);
//get companies that lasted ten years or more
const lastedTenYears = companies.filter((company, index) => (company.end - company.start >=10));
console.log(lastedTenYears);
//3. map()
var testMap = companies.map(function (company,index ) {
return company.name;
}); //Array(9) [ "Company One", "Company Two", "Company Three", "Company Four", "Company Five", "Company Six", "Company Seven", "Company Eight", "Company Nine" ]
testMap = companies.map(function (company ) {
return `${company.name } [${company.end} - ${company.start}]`;
}) //Array(9) [ "Company One [2003 - 1981]", "Company Two [2008 - 1992]", "Company Three [2007 - 1999]", "Company Four [2010 - 1989]", "Company Five [2014 - 2009]", "Company Six [2010 - 1987]", "Company Seven [1996 - 1986]", "Company Eight [2016 - 2011]", "Company Nine [1989 - 1981]" ]
console.log(testMap)
//4. sort()
//sort by start year
var sorted = companies.sort(function (a,b ) {
if (a.start > b.start){
return 1;
}else {
return -1;
}
});
sorted = companies.sort((a,b) => a >b ? 1 : -1);
//sort ages
sorted =ages.sort((a,b) => a-b);
console.log(sorted);
//5. reduce()
var total = ages.reduce(function (total, age) {
return total+age;
});
total = ages.reduce((total, age) => total +age);
console.log(total);
</script>
</body>
</html>
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