JavaScript Flow control – loop

Loop profile

  • There are three main types of loops in JS:
    • The for loop
    • The while loop
    • The do while loop
  • A set of statements that are executed repeatedly is called the body of a loop, and whether they can be executed continuously depends on the termination conditions of the loop
  • A statement consisting of a loop body and a loop termination condition is called a loop statement

The for loop

  • Grammatical structure

    • forInitialize a variable; Conditional expression; Operation expression) {// loop statements
}
// To initialize a variable, we use var to declare a normal variable, which is executed only once before the entire for loop is completed
// The conditional expression determines whether or not we execute each time through the loop, terminating the condition with true and continuing execution
// Operation expression, the code executed at the end of each loop
Copy the code

  • Chrome breakpoint test

    • Breakpoint test is to set a breakpoint on one line of your program, and the program will stop on this line during debugging.
    • Breakpoint testing can help us observe the program as it runs

  • The test method

    • In Chrome, call Up Sources
    • Find the test file
    • Set a breakpoint on a line of the program
    • Watch changes to monitor variables through watch
    • f11You can make the program run step by step

  • Execute the same code

  • Execute different code

  • A for loop can do something repeated something repeated

  • Double for loop

    • Syntactic structure conditional expressions

      • forInitialize a variable; Conditional expression; Operation expression) {forInitialize a variable; Conditional expression; Operation expression) {// loop statements}}// Each time the outer loop is executed, the inner loop executes until the conditional expression is false
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The while loop

  • Grammatical structure:

    • while(conditional expression) {/ / the loop body
    // Be sure to use a timer, otherwise you will enter an infinite loop
}
// If the conditional expression is judged to be true, the loop body continues
// You can make some complicated judgments, but you can use the for loop instead
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The do while loop

  • Grammatical structure

    • do {
   // The body of the loop is executed the first time regardless of whether the conditional expression is true
} while(Conditional expression)Copy the code

continue break

  • Continue Exits the loop and executes the rest of the loop
  • Break Breaks the entire loop

JavaScript naming conventions and syntax formats

  • The logo is clearly standardized
    • Variable names are usually nouns
    • Function names usually use verbs
  • Operator specification
    • Write a space to the left and right of the operator