JavaScript & Array groupBy All In One

JavaScript & Array groupBy All In One

Array.prototype.groupBy() ❌

// Arrow function
groupBy((element) => { /* ... */ } )
groupBy((element, index) => { /* ... */ } )
groupBy((element, index, array) => { /* ... */ } )

// Callback function
groupBy(callbackFn)
groupBy(callbackFn, thisArg)

// Inline callback function
groupBy(function(element) { /* ... */ })
groupBy(function(element, index) { /* ... */ })
groupBy(function(element, index, array){ /* ... */ })
groupBy(function(element, index, array) { /* ... */ }, thisArg)

Array.prototype.groupByToMap() ❌

// 

Array.prototype.group() 🧪

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/group

Array.prototype.groupToMap() 🧪

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/groupToMap

js get last element of the array

Array.prototype.at()

// Array.at()

const arr = [1, 2, 3, 4, 5];

let index = 1;
console.log(arr.at(index));
// 2

let lastIndex = -1;
console.log(arr.at(lastIndex));
// 5

// 等价于
console.log(`\n`,arr[1]);
// 2
console.log(arr[arr.length - 1]);
// 5

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at

refs

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/groupBy

https://developer.mozilla.org/en-US/docs/Glossary/Deep_copy

https://developer.mozilla.org/en-US/docs/Glossary/Shallow_copy

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