Web Development (beginner)-Python, JavaScript, and jquery loop statements

Looping StatementsI. Overview

There are two kinds of looping statements in Python, while,for;

There are four types of looping statements in JavaScript, while,do/while,for,for/in

jquery Loop Statements each

Second,pythonLooping Statements

2.1 For Loop

# A, Li = [1, 2, 3, 4]for I in Li:print (i)

# b, Li = [1, 2, 3, 4]for I, J in enumerate (Li, 1): Print (I, J) # Enumerate (li, 1) 1 for index starting from 1, default is null, represents starting from 0

# c, li1 = [1, 3, 5, 7]li2 = [2, 4, 6, 8]for I, J in Zip (Li1, li2): Print (i, j)

# d, do not cycle the dictionary through Dic.items (), the efficiency will be very low dic = {' A ': 1, ' B ': 2}for K in Dic:print (K, Dic.get (k)) # The above code, the equivalent of a dictionary key to the loop, equivalent to the next Face code: dic={' A ': 1, ' B ': 2}for K in Dic.keys (): Print (K, dic.get (k)) # for the value of the loop, that is, for the V in Dic.values () ...

2.2 While Loop

While True:pass # in Python except for none, ', [], {}, (), False, the others are true, that is. # for cyclic judgment: eg. flag# determines if true: while flag:# determines whether it is false: While not flag:

third, JavaScript loop statementA, while loop

var count = 0;while (Count < Ten) {Console.log (count); Count + +;} # JavaScript defines local variables with Var

B, Do/while

do{code block;} while (conditional statement)

C, for

var a = document.getElementById (' key '). Children;for (var i=0; i<a.length; i++) {var inp=a[i];    var at=inp.getattribute (' type ');    if (at== ' text ') {inp.setattribute (' value ', ' 123 '); Get the label for all type= ' text ' under id= ' key ' and set the value equal to ' 123 '.

D, for in

var C1 = document.getElementById (' I1 '). getElementsByTagName (' input '); for (var i in C1) {if (c1[i].checked) {c1[i].ch  Ecked=false;  }else{c1[i].checked=true; }}

Iv. jquery Loop Statements

Each statement:

$ (': Text '). each (function () {Console.log ($ (this). Val ());}); # $ (': Text ') ==> $ (' input[type= "text"] ')

Syntax rules: A collection of tags. each (anonymous function)

The above code means: Get the label of type= ' text ' in all INP tags and loop it, printing its value each time.

Jump out of the loop with return in jquery:

return true: Exit this loop and perform the next cycle, equivalent to the continue of other languages;

return false: Exits this layer loop, that is, exits the current each, equivalent to another language break;

Web Development (beginner)-Python, JavaScript, and jquery loop statements