javascript - 返回一个字符串而不是循环打印语句

Question

我是 Javascript 新手，我很好奇如何在字符串中存储值然后返回它。在下面的示例中，选择了 2 个数字，例如 2 和 8，程序应返回 2x1 =2、2x2=4，..... 一直到 2x8 =16。显然，这可以通过像我一样不断循环打印语句来完成，但是我如何能够将所有值存储在字符串中，然后返回字符串。

function showMultiples (num, numMultiples)
{
for (i = 1; i < numMultiples; i++)
  {
    var result = num*i;
    console.log(num + " x " + i + " = " + result+ "\n"); 
  }
}
console.log('showMultiples(2,8) returns: ' + showMultiples(2,8));
console.log('showMultiples(3,2) returns: ' + showMultiples(3,2));
console.log('showMultiples(5,4) returns: ' + showMultiples(5,4));

Answer 1

function showMultiples(num, numMultiples) {
  // the accumulator (should be initialized to empty string)
  var str = "";
  for (i = 1; i < numMultiples; i++) {
    var result = num * i;
    // use += to append to str instead of overriding it
    str += num + " x " + i + " = " + result + "\n";
  }
  // return the result str
  return str;
}

var mulOf5 = showMultiples(5, 10);

console.log("multiples of 5 are:\n" + mulOf5);

运算符+=将a值(右操作数)与左操作数的前一个值相加，并将结果存储在后面。所以这两行是相同的:

str = str + someValue;
str += someValue;