TypeError模块中的语句不让函数无第二个参数

Question

我想为String对象添加一个函数，它搜索所有字符串并返回我们想要查找的字的索引。当我不使用startIndex参数时，它不应该抛出第二个错误，因为这个语句typeof startIndex !== "undefined"让这个函数在没有startIndex的情况下工作。请纠正我，并感谢您的帮助。

String.prototype.allIndexOf = allIndexOfFunction; 

function allIndexOfFunction(string, startIndex) { 
    startIndex = startIndex || 0 
    var indexArr = []; 
    var sIndex = 0; 
    var baseString = this.concat(); 
    if (typeof string === "string" && typeof startIndex === "number" && startIndex >= 0) { 
     while(sIndex !== -1){ 
      sIndex = baseString.indexOf(string, startIndex); 
      if(sIndex !== -1){ 
       indexArr.push(sIndex); 
       startIndex = startIndex + sIndex +1; 
      } 
     } 
    } 
    try { 
     if (typeof string !== "string") { 
      throw "First parameter must be a string type"; 
     } 
     else if (typeof startIndex !== "number" || typeof startIndex !== "undefined") { 
      throw "Second parameter must be a number type"; 
     } 
     else if (startIndex <= 0) { 
      throw "Second parameter must be equal or bigger than 0"; 
     } 
    } catch(err) { 
     console.log(err); 
    } 

    return indexArr; 
} 
//TEST 
var a = "Lorem ipsum dolor sit Buzz, consectetur Buzz elit. Quod vero voluptatibus Buzz error deserunt libero, Buzz incidunt Buzz facere! A!"; 
var test = a.allIndexOf("Buzz"); 
console.log("Searching indexes of \"Buzz\" word in string -> " + a); 
console.log(test); 

Answer 1

简单的问题。你的逻辑是不完全正确 - 你需要的，而不是OR：

你一个行更改为：

else if (typeof startIndex !== "number" && typeof startIndex !== "undefined") {

而且，由于你默认为0，如果没有定义的startIndex，那么你就不要根本不需要第二个条件测试。

你可以看到它运行如下预期：

String.prototype.allIndexOf = allIndexOfFunction; 
 

 
function allIndexOfFunction(string, startIndex) { 
 
    startIndex = startIndex || 0 
 
    var indexArr = []; 
 
    var sIndex = 0; 
 
    var baseString = this.concat(); 
 
    if (typeof string === "string" && typeof startIndex === "number" && startIndex >= 0) { 
 
    while(sIndex !== -1){ 
 
     sIndex = baseString.indexOf(string, startIndex); 
 
     if(sIndex !== -1){ 
 
     indexArr.push(sIndex); 
 
     startIndex = startIndex + sIndex +1; 
 
     } 
 
    } 
 
    } 
 
    try { 
 
    if (typeof string !== "string") { 
 
     throw "First parameter must be a string type"; 
 
    } 
 
    else if (typeof startIndex !== "number") { 
 
     throw "Second parameter must be a number type"; 
 
    } 
 
    else if (startIndex <= 0) { 
 
     throw "Second parameter must be equal or bigger than 0"; 
 
    } 
 
    } catch(err) { 
 
    console.log(err); 
 
    } 
 

 
    return indexArr; 
 
} 
 
//TEST 
 
var a = "Lorem ipsum dolor sit Buzz, consectetur Buzz elit. Quod vero voluptatibus Buzz error deserunt libero, Buzz incidunt Buzz facere! A!"; 
 
var test = a.allIndexOf("Buzz"); 
 
console.log("Searching indexes of \"Buzz\" word in string -> " + a); 
 
console.log(test);