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Question

Dies ist ein Codeausschnitt aus Kapitel 3 von 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

So habe ich es mir erklärt. Aber ich kann nicht wirklich verstehen, warum 1024 Somoene zurückgegeben wird. Können Sie mir helfen, es aufzuschlüsseln?

/* 
    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));


*/

Ich erwarte Ergebnis * = Basis oder Ergebnis = Ergebnis * Basis. Ich weiß, dass mir in der Iteration etwas fehlt.

Answer 1

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

看来你已经明白这个错误的后果了。请注意，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 值相乘，然后将其用于下一次计算。所以就会是这样的。

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