How to declare an array
The declaration of an array in S can be declared in several ways
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var tmp = []; Shorthand mode
var tmp = new Array (); Direct New One
var tmp = Array (); Or new, you can.
In the new array, you can pass in a parameter that represents the initialization length of the array
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When new, pass in a parameter representing the initialization array length
var tmp = new Array (3);
alert (tmp.length); 3
But if you want to create an array of only one element 3, then using the new method is not possible because the system will use the 3 you pass in as the length of the array unless you use quotation marks as a string, as
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var tmp = new Array (' 3 ');
Alert (TMP); 3
We can create an array using the shorthand mode so that we can create an array with only one number element 3
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var tmp = [3]
Alert (typeof tmp[0]); Number
You can also initialize multiple elements, and the value of an element can be any type
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Create an array in minimalist mode
The elements of an array can be any one of the data types
var tmp = [3,true,8.5,{' name ': ' Lizhong '},[' a ', ' B ']];
alert (tmp.length); 5
Unshift inserts an element before the first element of the array
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Inserts an element before the first element of the array using Unshift
Returns the length of an array
var tmp = [' A ', ' B '];
var len = tmp.unshift (' C ');
alert (len); 3
Alert (TMP); C,a,b
You can also insert multiple elements at once, sequentially from the left
Copy Code code as follows:
Inserts an element before the first element of the array using Unshift
Returns the length of an array
var tmp = [' A ', ' B '];
var len = tmp.unshift (' C ', ' d ');
alert (len); 4
Alert (TMP); C,d,a,b
Second, shift pops the first element of the array, returning the element value that was ejected
Small example:
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Use shift to eject the first element of the array
Returns the value of the element being ejected
var tmp = [' A ', ' B ', ' C '];
var val = Tmp.shift ();
Alert (val); A
Alert (TMP); B,c
If it is an empty array:
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Use shift to eject the first element of the array
Returns the value of the element being ejected
var tmp = [];
var val = Tmp.shift ();
Alert (val); Undefined
Alert (TMP); Empty
Third, push add element at end of array
In contrast to unshift, push adds an element to the end of the array, returning the length of the array after the element is added
Copy Code code as follows:
Add multiple elements to the end of an array using push
Returns the latest array length
var tmp = [' A ', ' B ', ' C '];
var len = Tmp.push (' d ');
alert (len); 4
Alert (TMP); A,b,c,d
You can also add more than one element at a time
Copy Code code as follows:
Add multiple elements to the end of an array using push
Returns the latest array length
var tmp = [' A ', ' B ', ' C '];
var len = Tmp.push (' d ', ' e ', ' f ');
alert (len); 6
Alert (TMP); A,b,c,d,e,f
Four, pop function delete Array end element
In contrast to shift, the pop pops up with the end element of the array, returning the element value that was ejected
Copy Code code as follows:
Use pop to eject array end element
Returns the value of the element being ejected
var tmp = [' A ', ' B ', ' C '];
var val = Tmp.pop ();
Alert (val); C
Alert (TMP); A,b
If the array is empty, return undefined
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Use pop to eject array end element
Returns the value of the element being ejected
var tmp = [];
var val = Tmp.pop ();
Alert (val); Undefined
Alert (TMP); Empty
Using the above four functions, we can do some queue processing, the specific case will not write code.
The push function can actually be done as well.
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var tmp = [' A ', ' B ', ' C '];
Tmp[tmp.length] = ' d ';
Alert (TMP); A,b,c,d
Note: The above four functions unshift, shift, pop, push function actions are modified on the array itself.
