Essayez de comprendre les réponses aux extraits de code du livre Eloquent JavaScript

Question

Il s'agit d'un extrait de code du chapitre 3 d'Eloquent JavaScript.

const power = function(base, exponent) {
  let result = 1;
  for (let count = 0; count < exponent; count++) {
    result *= base;
  }
  return result;
};
console.log(power(2, 10));
// 1024

C'est ainsi que je me l'ai expliqué. Mais je ne comprends pas vraiment pourquoi 1024 somoene est renvoyé. Pouvez-vous m'aider à le décomposer ?

/* 
    Explanation of code above.

     - We created a function named power. We used a function expression notation to create it. 
     
     - power has two parameters base and exponent.

     - the body of the function contains the code that the function will execute. 

    - the body does the following:

        1. declares a variable called result which has a value of 1.
        
        2. There is a for loop. Here are the parts of the for loop:

            - The intializer: the variable count is declared and assigned a value of 0

            - We are looking at the condition to see if it is truthy. The condition is whether count is greater than exponent. The loop will continue to iterate until this condition is truthy.

            - The incrementer: count will go up by 1 each iteration of the loop

            - The body of the for loop (the code to be executed) states that the result variable is equal to result *= base OR result = result * base 
    
    - then the function will return the value of result 

    - we are done with the function 

    - outside of the function we invoke it using console.log() and pass it the arguments 2 and 10 (base, exponent). 

    - The computer plugs the arguments into the function. The computer evaluates the condition in the for loop to see if its truthy. Basically, the computer asks is count < exponent? Count = 0 and exponent = 10. So the condition evaluates to falsey. 


    const power = function (2, 10) {
    let result = 1;
    for (let count = 0; 11 < 10; count++) {
                    1   10
                    2   10
                    3   10
                    4   10
                    5   10
                    6   10
                    7   10
                    8   10
                    9   10
                    10  10
                    11  10
                    
        result *= base; => 2 = 2 * 10
    }
    return result;

};

console.log(power(2,10));


*/

J'attends le résultat * = base, ou le résultat = résultat * base. Je sais qu'il me manque quelque chose dans l'itération.

Answer 1

for(let count = 0; count < exponent; count++) {
  result *= base;
}

Il semble que vous compreniez déjà les conséquences de cette erreur. Notez que les valeurs count 变量仅用于控制循环的迭代次数。每次迭代时，您都会更新 result 变量以包含新值，方法是将其与 base sont multipliées puis utilisées pour le calcul suivant. Ce sera donc comme ça.

1 * 2 = 2
2 * 2 = 4
4 * 2 = 8
8 * 2 = 16
16 * 2 = 32
32 * 2 = 64
64 * 2 = 128
128 * 2 = 256
256 * 2 = 512
512 * 2 = 1024