Seventh Chapter-javascript Arrays

7.1 Arrays

①javascript arrays are used in many ways, and elements in an array do not have to be exactly the same type

Two ways to construct a ② array:

A. Constructors for arrays

var arrayname=new array ()///empty array var arrayname=new array (4)/////Length 4 array var arrayname=new array ("Thomas", "Roger",-3, " Plastic "); Array of 4 elements

B. Array literals notation

var arrayname=[];//empty array var arrayname=["Thomas", true,-3];//three elements of an array var arrayname=[3];//an array of elements

7.2 Properties of an array (because the array is an object in JavaScript, it has properties and methods)

This is just a description of the length property, which is described in the other sections later.

var stu=["Thomas", "Roger", "Amber", "Jen"];stu.length=2;//shorten the array, now the array has only the first two elements stu.length=7;//an array of growth, adding 5 elements at the end, Their values are undefined. Stu[9]= "Mary";//increment array, length 10, index 9 that is, tenth element value is Mary, others are undefined

7.3 Methods of arrays

①sort method

②concat () method

③slice (Start,stop) method: Gets an array of sub-arrays, custom start and end indexes, sub-arrays include start index, no end index.

④splice (Start delete index, delete element number, [added element]) method

var arr=["Orange", "apple", "pear", "Grape"];var arr1=arr.splice (2,1, "watermelon", "plum"), arr1=["Orange", "Apple", " Watermelon "," plum "," grape "];

Seventh Chapter-javascript Arrays