<!DOCTYPE html>
<html>
<head>
<meta name="description" content="joins with map-filter-reduce">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>JS Bin</title>
</head>
<body>
<script id="jsbin-javascript">
'use strict';
var students = [{
id: 1,
name: 'Carlos'
}, {
id: 2,
name: 'Lola'
}, {
id: 3,
name: 'Max'
}];
var tests = [{
id: 1,
studentID: 1,
title: 'Fractals'
}, {
id: 2,
studentID: 1,
title: 'Javascript'
}, {
id: 3,
studentID: 2,
title: 'Fractals'
}, {
id: 4,
studentID: 3,
title: 'Javascript'
}];
var result = students.map(function (student) {
var reducer = function reducer(count, test) {
return test.studentID === student.id ? count + 1 : count;
};
var testCount = tests.reduce(reducer, 0);
return {
studentName: student.name,
testCount: testCount
};
});
var result2 = students.map(function (student) {
var filter = tests.filter(function (test) {
return test.studentID === student.id;
});
var testCount = filter.length;
return {
studentName: student.name,
testCount: testCount
};
});
console.log(result);
console.log(result2);
</script>
<script id="jsbin-source-javascript" type="text/javascript">const students = [
{
id: 1,
name: 'Carlos'
},
{
id: 2,
name: 'Lola'
},
{
id: 3,
name: 'Max'
}
];
const tests = [
{
id: 1,
studentID: 1,
title: 'Fractals'
},
{
id: 2,
studentID: 1,
title: 'Javascript'
},
{
id: 3,
studentID: 2,
title: 'Fractals'
},
{
id: 4,
studentID: 3,
title: 'Javascript'
}
];
const result = students.map( student => {
const reducer = (count, test) =>
test.studentID === student.id ? count + 1 : count;
const testCount = tests.reduce(reducer, 0);
return {
studentName: student.name,
testCount: testCount
};
});
const result2 = students.map( student => {
const filter = tests.filter(test =>
test.studentID === student.id);
const testCount = filter.length;
return {
studentName: student.name,
testCount: testCount
};
});
console.log(result);
console.log(result2);</script></body>
</html>