1. Array deduplication

1, Superimpose the new Set() method from()

A string or numeric array can be de-duplicated directly using the FROM method.

var plants = ['Saturn'.'Earth'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
var uniquePlants = Array.from(new Set(plants)); 
console.log(uniquePlants); // [ 'Saturn', 'Earth', 'Uranus', 'Mercury', 'Venus', 'Mars', 'Jupiter' ]
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2, spread operator (…)

Extended operators are one of the big innovations of ES6, along with many powerful features.

var plants = ['Saturn'.'Earth'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
var uniquePlants = [...new Set(plants)]; 
console.log(uniquePlants); // [ 'Saturn', 'Earth', 'Uranus', 'Mercury', 'Venus', 'Mars', 'Jupiter' ]
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2. Replace a specific value in the array

The splice() method adds/removes items from/to the array and returns the deleted items. This method changes the original array. Pay special attention to where the values are inserted!

var plants = ['Saturn'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
var result = plants.splice(2.1.'www.shanzhonglei.com')
console.log(plants); // ['Saturn','Uranus','www.shanzhonglei.com','Mercury','Venus','Earth','Mars','Jupiter']
console.log(result); // ['Mercury']
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3. There is no mapping array for map()

Let’s start with the Map method. The map() method returns a new array whose elements are the values of the original array elements. It processes the elements in the same order as the original array elements. Note: Map () does not alter the original array, nor does it detect an empty array. Let’s implement an array map without a map:

var plants = [
    { name: "Saturn" },
    { name: "Uranus" },
    { name: "Mercury" },
    { name: "Venus"},]var plantsName = Array.from(plants, ({ name }) = > name);
console.log(plantsName); // [ 'Saturn', 'Uranus', 'Mercury', 'Venus' ]
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4. Empty array

If you want to empty an array, just set the length of the array to 0, well, that’s a little bit easy.

var plants = ['Saturn'.'Earth'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
plants.length = 0;
console.log(plants); / / []
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5. Convert arrays to objects

The fastest way to convert an array to an object is the spread operator (…). .

var plants = ['Saturn'.'Earth'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
varplantsObj = {... plants }console.log(plantsObj); // {'0': 'Saturn','1': 'Earth', '2': 'Uranus','3': 'Mercury','4': 'Venus','5': 'Earth','6': 'Mars','7': 'Jupiter'}
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6. Populate the array with data

If we need to fill an array with some data, or if we need a data with the same value, we can use fill().

var plants = new Array(8).fill('8');
console.log(plants); // ['8', '8','8', '8','8', '8','8', '8','8', '8','8']
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7. Merge arrays

Of course you would think of the concat() method, but oh, the spread operator (…) It’s also nice, and this is another use of extension operators.

var plants1 = ['Saturn'.'Earth'.'Uranus'.'Mercury'];
var plants2 = ['Venus'.'Earth'.'Mars'.'Jupiter'];
console.log([...plants1, ...plants2]); // ['Saturn', 'Earth','Uranus', 'Mercury','Venus', 'Earth','Mars', 'Jupiter']
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Intersection of two arrays

To ask for the intersection of two arrays, first make sure the arrays are not duplicated, and then use the filter() and includes() methods.

var plants1 = ['Saturn'.'Earth'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
var plants2 = ['Saturn'.'Earth'.'Uranus'];
var alonePlants = [...new Set(plants1)].filter(item= > plants2.includes(item));
console.log(alonePlants); // [ 'Saturn', 'Earth', 'Uranus' ]
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Delete false values from array

We often need to remove false values when processing data. In Javascript, false values are false, 0, “”, null, NaN, undefined

var plants = ['Saturn'.'Earth'.null.undefined.false."".NaN.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
var trueArr = plants.filter(Boolean);
console.log(trueArr); // ['Saturn', 'Earth','Uranus', 'Mercury','Venus', 'Earth','Mars', 'Jupiter']
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Get a random value from the array

We can get a random index number based on the length of the array.

var plants = ['Saturn'.'Earth'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
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The lastIndexOf() method

LastIndexOf () helps us find the index of the last occurrence of the element.

var plants = ['Saturn'.'Earth'.'Uranus'.'Mercury'.'Venus'.'Earth'.'Mars'.'Jupiter'];
console.log(plants.lastIndexOf('Earth')) / / 5
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12. Add all the values in the array

The reduce() method takes a function as an accumulator, and each value in the array (from left to right) starts to shrink and eventually evaluates to a value.

var nums = [1.2.3.4.5];
var sum = nums.reduce((x, y) = > x + y);
console.log(sum); / / 15
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