How to write python, JavaScript and jQuery Loop statements in Web Development

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Circular statement I. Overview

There are two kinds of loop statements in python, while,for

There are four kinds of loop statements in JavaScript, while,do/while,for,for/in

JQuery Loop statement each

II. Python Loop statement

2.1 for cycle

# 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) represents index starting from 1, default is empty 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 (), it will be very inefficient dic = {'averse: 1,' baked: 2} for k in dic: print (k, dic.get (k)) # in the above code, it is equivalent to cycling the key of the dictionary. It is equivalent to the following code: dic= {'averse: 1,' baked: 2} for k in dic.keys (): print (k, dic.get (k)) # for the loop of the value, that is, for v in dic.values ()... 2.2 while loop while True: pass # is true in python except none,'', [], {}, (), False, and all other values are true, that is, True. # for loop judgment: eg. Flag# determines whether it is true: while flag:# judges whether it is false: while not flag: 3. JavaScript loop statement a, while loop var count = 0 position while (count < 10) {console.log (count); count + +;} # JavaScript defines local variables with varb, do/whiledo {code block;} while (conditional statement) c, forvar a = document.getElementById ('key'). Children;for (var item0; I $(' input [type = "text"]')

Syntax rules: tag collection .each (anonymous function)

The above code means: take the type='text', tag in all the inp tags and loop through it, printing its value each time.

Return for jumping out of the loop in jQuery:

Return true: exit this loop and execute the next loop, which is equivalent to continue in other languages

Return false: exit this loop, that is, exit the current each, which is equivalent to break in other languages

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