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85 lines
1.7 KiB
Markdown
85 lines
1.7 KiB
Markdown
---
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date: 20200827
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id: 513ff88e-d0c9-41d1-8416-57a4aff100c7
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title: JavaScript higher-order functions
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---
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# Examples
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Functions that operate on other functions, either by taking them as
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arguments or by returning them, are called higher-order functions. They
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allow us to abstract over actions as well as values. There are several
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types, here are some examples.
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## Functions that create new functions
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``` javascript
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function greaterThan(n) {
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return m => m > n;
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}
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let greaterThan10 = greaterThan(10);
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console.log(greaterThan10(11));
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```
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## Functions that change other functions
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``` javascript
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function noisy(f) {
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return (...args) => {
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console.log("calling with", args);
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let result = f(...args);
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console.log("called with", args, ", returned", result);
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return result;
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};
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}
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noisy(Math.min)(3, 2, 1);
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```
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## Functions that provide new types of flow control
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``` javascript
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function unless(test, then) {
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if (!test) then();
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}
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repeat(3, n => {
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unless(n % 2 == 1, () => {
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console.log(n, "is even");
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});
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});
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```
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## ES6
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### Funciton properties
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1. name
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The `name` property contains the function's name:
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``` javascript
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function foo() {};
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console.log(foo.name); // foo
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let func1 = function () {};
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console.log(func1.name); // func1
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let func4;
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func4 = function () {};
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console.log(func4.name); // func4
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```
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1. Default values
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``` javascript
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let [func1 = function () {}] = [];
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console.log(func1.name); // func1
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let { f2: func2 = function () {} } = {};
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console.log(func2.name); // func2
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function g(func3 = function () {}) {
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return func3.name;
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}
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console.log(g()); // func3
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```
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