如何从JavaScript中的循环中使用整数填充数组

Question

I just signed up in codewars and I'm trying the first kata. This is the question:

Write a function to multiply a number (x) by a given number (y) a certain number of times (n). The results are to be returned in an array. eg. multiplyBy(2, 4, 6); The output is: [8, 32, 128, 512, 2048, 8192]

I believe my code is write, when I do console.log I get the array that the exercise is asking for, but it won't let me proceed. I'd appreciate some help, thanks!

var array  = [];
function multiplyBy(x, y, n) {
while (x<2049){
var z = x*y*n;
var x = z;
array.push(z)
}
}
multiplyBy(2,2,2);
console.log(array);
return array;

Answer 1

You have a few things going on outside your function which make it only work one time. Make sure that you keep everything inside the function until the last return

function multiplyBy(x, y, n) {
    var array = []; // var this inside your function
    for (; n > 0; --n) { // the loop is only supposed to happen n times
        x = x * y; // you can reuse this variable (x)
        array.push(x);
    }
    return array; // return statement should be inside your function
}

// example of logging the returned value
console.log(multiplyBy(2, 4, 6)); // [8, 32, 128, 512, 2048, 8192]

Your while loop also was hardcoded to x<2049 , but this isn't always the case as it depends on the n parameter given to the function

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it won't let me proceed

There are 3 issues in the code you posted that probably prevent you from proceeding,

1. The return array is probably throwing a syntax error because it's outside a function
2. In your code, calling multiplyBy several times appends the new values onto the end of the previous array
3. They are probably testing your function against other sets of values to check it works as expected, which is not true in your function, ie you gave the example inputs of 2, 4, 6 but used 2, 2, 2 in your own code

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As a final note, try to get into the habbit of indenting your code, it'll save you headaches reading it later as it lets you quickly see where blocks begin and end

Answer 2

Your return is outside the function. And all calls to multiplyBy populate the same array. And your logic is flawed.

Probably, it should be

 function multiplyBy(x, y, n) { var array = []; while (n--) array.push(x *= y) return array; } console.log(multiplyBy(2,4,6)); 

Or, in ECMAScript 6,

var multiplyBy = (x, y, n) => Array(n).fill().map(a => x*=y);

Answer 3

ramove最后的return，必须在函数中使用它来返回某些内容，如果不使用该函数将返回undefined。

Answer 4

Look at this (single-line solution):

function multiplyBy(x,y,n) {
    return Array.apply(null, new Array(n)).map(function(v, i) { return x * Math.pow(y, i + 1); });
}

DEMO