javascript提示返回类型始终是对象？

Question

 function check_color(){ color_input = prompt("I am thinking of one of these colors: \\n\\n"+ "blue, cyan, gold, gray, magenta, orange, red, white, yellow \\n\\n"+ "What color am I thinking of?"); if(color_input != null || color_input != undefined){ if(typeof (color_input) != 'string') { alert("This is not any color. \\n\\n"+ "Please enter color in text format"); return false; } if(colors.indexOf(color_input) < 0){ alert("Sorry, i don't recognize your color. \\n\\n"+ "Please try again"); return false; } } else{ alert("Please enter some input"); return false; } } 

为什么在尝试运行此代码时总是执行first-if块？ 有人可以解释一下吗？

Answer 1

“颜色”在哪里if（colors.indexOf（color_input）

我在这里收到控制台错误。 请添加颜色数组

Answer 2

我不确定这个问题，但是在jsFiddle中，此代码段按预期工作：

function check_color() {
   color_input = prompt("I am thinking of one of these colors: \n\n" +
         "blue, cyan, gold, gray, magenta, orange, red, white, yellow \n\n" +
         "What color am I thinking of?");

   colors = ["blue", "cyan", "gold", "gray", "magenta", "orange", "red", "white", "yellow"];

  if (color_input != null) {

     if (typeof(color_input) != 'string') {
        console.log("This is not any color. \n\n" +
           "Please enter color in text format");
        return false;
     }

     if (colors.indexOf(color_input) < 0) {
        console.log("Sorry, i don't recognize your color. \n\n" +
           "Please try again");
        return false;
     }

     console.log("your color:" + color_input);
  } else {
     console.log("Please enter some input");
     return false;
  }
}
check_color();

我必须将颜色数组添加到代码段中（我假设您在其他地方有它）。 我还取出了“ || undefined”，因为提示符仅返回字符串或null。

因此，您可以这样简化代码：

function check_color() {
   color_input = prompt("I am thinking of one of these colors: \n\n" +
      "blue, cyan, gold, gray, magenta, orange, red, white, yellow \n\n" +
      "What color am I thinking of?");

   colors = ["blue", "cyan", "gold", "gray", "magenta", "orange", "red",     "white", "yellow"];

   if (color_input) { // null would be false
      if (colors.indexOf(color_input) < 0) {
         console.log("Sorry, i don't recognize your color. \n\n" +
            "Please try again");
         return false;
      }

      console.log("your color:" + color_input);
   } else {
      console.log("Please enter some input");
      return false;
   }
}
check_color();