检查一个值是否未初始化总是返回未初始化的值，即使它已初始化

Question

我正在尝试类似jquery的脚本，支持选择器，显示，隐藏，文本和html方法。运行测试时，无论我调用哪个方法，它总是抛出一个自定义的"no Element selected";错误。我该如何解决这个问题?完整的代码在这里——>https://jsfiddle.net/7ado13vg/

相关代码在

下面

var storingAttributes = {};
class MONEY {
constructer(string) {
try {
//check for action
if (string != null) {
//Check Selection Type
storingAttributes.selectorArray = string.split('')
if (storingAttributes.selectorArray[0] == '#') {
storingAttributes.selectionType = 'id';
storingAttributes.selectorArray.splice(0, 1);
}
if (storingAttributes.selectorArray[0] == '.') {
storingAttributes.selectionType = 'class';
storingAttributes.selectorArray.splice(0, 1);
}
if (storingAttributes.selectorArray[0] != '#' && storingAttributes.selectorArray[0] != '.') {
storingAttributes.selectionType = 'tag';
}
//Select Elem
if (storingAttributes.selectionType == 'id') {
storingAttributes.selectedElem = document.querySelector(string);
}
if (storingAttributes.selectionType == 'class') {
storingAttributes.selectedElem = document.querySelectorAll(string);
}
if (storingAttributes.selectionType == 'tag') {
storingAttributes.selectedElem = document.querySelectorAll(string);
}
}
} catch (error) {
}
}
//The reason I checked what was being selected is because querySelectorAll returns an array, and I do not believe that ids are supported
//trying to use my method 'show'
show() {
try {
if (typeof storingAttributes.selectedElem == 'undefined' || storingAttributes.selectedElem == null) {
throw "No Element Selected";
} else {
if (storingAttributes.selectionType == 'tag') {
for (n = 0; n < storingAttributes.selectedElem.length; ++n) {
storingAttributes.selectedElem[n].style.display = 'block';
}
return;
}
if (storingAttributes.selectionType == 'class') {
for (n = 0; n < storingAttributes.selectedElem.length; ++n) {
storingAttributes.selectedElem[n].style.display = 'block';
}

return;
}

if (storingAttributes.selectionType == 'id') {
storingAttributes.selectedElem.style.display = 'block';
return;
}
}
} catch (e) {
console.log(e);
}
}
}

可以看到，constructor只是在对象storingAttributes

中为selectionType、selectedElem和selectorArray

赋值/初始化一个值当您记录storingAttributes时，它返回一个空对象。

Answer 1

下面的代码替换了您发布的代码，以显示编写它是多么简单，并且不会错误地使用try/catch。

我知道它不能回答你的问题，但是你正在使用的代码实在是不必要的过多，如果不重构它，很难筛选它来找到你的问题。代码越简单越容易调试。

var storingAttributes = {};
// Just test for the non-existance of a value
if (!storingAttributes.selectedElem) {
throw "No Element Selected";
} else {
// switch is more concise when you have a single value to 
// check against multiple possible values
switch (storingAttributes.selectionType){
case "tag":
// And since you want to do the exact same code if
// it's "tag" or "class", we'll allow fall through here
case "class":
// The Array.prototype.forEach method makes looping much simpler
storingAttributes.selectedElem.forEach(function(item){
item.classList.add("block");
});
break;  
case "id":
storingAttributes.selectedElem.classList.add("block");
}
}

/* Avoid inline styles which lead to duplication of code.
Instead, use CSS classes where possible. */
.block { display:block; }