This article mainly shares with you the array functions and precautions in js. First, let's share with you what array objects are in js. I hope it can help you.
What are the array objects of js
push — Add one or more elements to the end of the array and return the new length.
pop — Delete and return the last element of the array
shift — Delete and return the first element of the array
unshift —Adds one or more elements to the beginning of the array and returns the new length.
slice — Return selected elements from an existing array
sort — Sort the elements of the array
join —Put all elements of the array into a string. Elements are separated by the specified delimiter.
concat — Concatenates two or more arrays and returns the result.
reverse —Reverse the order of elements in an array.
splice — Removes elements and adds new elements to an array.
Usage Notes
push and unshift both return the new length
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pop , shift deletion returns the deleted value
var Arr1 = ['11','22','33'] var a = Arr1.push('44'); console.log(a); //4 console.log(Arr1);//["11", "22", "33", "44"] var c = Arr1.pop(); console.log(c); //44 console.log(Arr1);//["11", "22", "33"] var d = Arr1.pop(); console.log(d);//33 console.log(Arr1);//["11", "22"] var Arr2 =['a','b','c'] var b =Arr2.unshift('-a'); console.log(b); //4 console.log(Arr2); // ["-a", "a", "b", "c"] var e = Arr2.shift(); console.log(e); //-a console.log(Arr2); // ["a", "b", "c"] var f = Arr2.shift(); console.log(f); //a console.log(Arr2); // ["b", "c"]
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slice and splice
slice returns a new array that has nothing to do with the original array and will not affect the source object
parameters (start , end) where to start (if it is a negative number, count from the end), and where to end (if it is a negative number, count from the end)var Arr1 = ['11','22','33'] var a = Arr1.slice(0); console.log(a); Arr1[0] = '111'; console.log(a); console.log(Arr1);
splice will split the source object
arrayObject.splice(index,howmany,item1,.....,itemX) index 必需。整数,规定添加/删除项目的位置,使用负数可从数组结尾处规定位置。 howmany 必需。要删除的项目数量。如果设置为 0,则不会删除项目。 item1, ..., itemX 可选。向数组添加的新项目 var Arr1 = ['11','22','33','44','55']; var a = Arr1.splice(1,5); console.log(a); // ["22", "33", "44", "55"] console.log(Arr1); //["11"] var Arr1 = ['11','22','33','44','55']; var a = Arr1.splice(1,5,'66','77','88'); console.log(a);["22", "33", "44", "55"] console.log(Arr1); ["11", "66", "77", "88"]
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sort
arrayObject.sort(sortby) sortby 可选。规定排序顺序。必须是函数。 function sortNumber(a,b) { return -(a - b) } var arr = new Array(6) arr[0] = "10" arr[1] = "5" arr[2] = "40" arr[3] = "25" arr[4] = "1000" arr[5] = "1" console.log(arr.sort(sortNumber))//["1000", "40", "25", "10", "5", "1"]
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Conversion of strings and arrays
var arr = new Array(6) arr[0] = "10" arr[1] = "5" arr[2] = "40" arr[3] = "25" arr[4] = "1000" arr[5] = "1" var a = arr.join('-'); console.log(a);//10-5-40-25-1000-1 var b = a.split('-'); console.log(b);//["10", "5", "40", "25", "1000", "1"]
concat
will generate a new array, not Affects the original array
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