避免JavaScript中的重复方式

huangapple
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英文:

Avoid duplication in JavaScript way

问题

我想防止重复添加数值。

如果（this.sQuestions.findIndex（（item）=>
item.question.replace（/\s/g，""）.toLowerCase（）===
this.quest.replace（/\s/g，""）.toLowerCase（））>0）
{
this.isQuestionExist = true;
}
否则 {
//保存功能
}

它有效，除了sQuestions[0]元素，为什么？

英文:

I would like to prevent for adding duplicate values.

  1. if (this.sQuestions.findIndex((item) => 
  2.     item.question.replace(/\s/g, "").toLowerCase() ===  
  3.         this.quest.replace(/\s/g, "").toLowerCase()) > 0) 
  4. {
  5.   this.isQuestionExist = true;
  6. }
  7. else {
  8.   //save function
  9. }

It's working except the sQuestions[0] element, Why?.

答案1

得分: 3

建议使用Set来实现此目的。正如文档所述：

Set对象允许您存储任何类型的唯一值，无论是原始值还是对象引用。

文档中的示例：

  1. const set1 = new Set([1, 2, 3, 4, 5]);
  3. console.log(set1.has(1));
  4. // 期望输出：true
  6. console.log(set1.has(5));
  7. // 期望输出：true
  9. console.log(set1.has(6));
  10. // 期望输出：false

希望这能帮助您！

英文:

I suggest to use Set for this purpose. As the documentation states:

> The Set object lets you store unique values of any type, whether primitive values or object references.

Example from the documentation:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

  1. const set1 = new Set([1, 2, 3, 4, 5]);
  3. console.log(set1.has(1));
  4. // expected output: true
  6. console.log(set1.has(5));
  7. // expected output: true
  9. console.log(set1.has(6));
  10. // expected output: false

<!-- end snippet -->

I hope this helps!

答案2

得分: 1

你正在比较是否大于 0，如果数组中找不到该项，函数将返回 -1，因此应该与 -1 进行比较。

这将会起作用。

  1. if (this.sQuestions.findIndex((item) => item.question.replace(/\s/g, "").toLowerCase() === this.quest.replace(/\s/g, "").toLowerCase()) !== -1) {
  2.   this.isQuestionExist = true;
  3. }
  4. else {
  5.   // 保存函数
  6. }
英文:

You are comparing against &gt; 0 if the item is not found in the array, the function will return -1 so it should be compared against -1

This will be working.

  1. if (this.sQuestions.findIndex((item) =&gt; item.question.replace(/\s/g, &quot;&quot;).toLowerCase() === this.quest.replace(/\s/g, &quot;&quot;).toLowerCase()) !== -1) {
  2.   this.isQuestionExist = true;
  3. }
  4. else {
  5.   //save function
  6. }

答案3

得分: 1

根据您的问题，您可以尝试

  1. let uniqueQuestions = new Set(this.sQuestions)
英文:

According to your question, you can try

  1. let uniqueQuestions = new Set(this.sQuestions)

答案4

得分: 1

为了性能和清晰度的原因，您应该将问题索引在一个专用的结构中，比如Map：

  1. function getKey(question)
  2. {
  3.     return question.replace(/\s/g, '').toLowerCase()
  4. }
  6. var question1 = {
  7.     ID: 1,
  8.     text: 'What time is it?'
  9. }
  11. var question2 = {
  12.     ID: 2,
  13.     text: 'Where is it?'
  14. }
  16. var question3 = {
  17.     ID: 3,
  18.     text: 'What is it?'
  19. }
  21. var questions = new Map()
  22. questions.set(getKey(question1.text), question1)
  23. questions.set(getKey(question2.text), question2)
  24. questions.set(getKey(question3.text), question3)
  26. var quest = 'Where is it?'
  27. var match = questions.get(getKey(quest))
  28. console.log(match)
  30. quest = 'WTF?'
  31. match = questions.get(getKey(quest))
  32. console.log(match)

结果：

  1. { ID: 2, text: 'Where is it?' }
  2. undefined
英文:

For performance and clarity reasons you should index your questions in a dedicated structure like a Map:

  1. function getKey(question)
  2. {
  3. 	return question.replace(/\s/g, &#39;&#39;).toLowerCase()
  4. }
  6. var question1 = {
  7. 	ID: 1,
  8. 	text: &#39;What time is it?&#39;
  9. }
  11. var question2 = {
  12. 	ID: 2,
  13. 	text: &#39;Where is it?&#39;
  14. }
  16. var question3 = {
  17. 	ID: 3,
  18. 	text: &#39;What is it?&#39;
  19. }
  21. var questions = new Map()
  22. questions.set(getKey(question1.text), question1)
  23. questions.set(getKey(question2.text), question2)
  24. questions.set(getKey(question3.text), question3)
  26. var quest = &#39;Where is it?&#39;
  27. var match = questions.get(getKey(quest))
  28. console.log(match)
  30. quest = &#39;WTF?&#39;
  31. match = questions.get(getKey(quest))
  32. console.log(match)

Result:

  1. { ID: 2, text: &#39;Where is it?&#39; }
  2. undefined

答案5

得分: 1

你可以使用 some 方法来检查数组中是否存在数据：

  1. if (!this.sQuestions.some(q => q.question == newQuestion)) 
  2. {
  3.   this.isQuestionExist = true;
  4. }
  5. else {
  6.   // 保存函数
  7. }

一个示例：

  1. let arr = [1, 2, 3, 4, 5];
  2. console.log(`arr has 1`, arr.some(s => s == 1))
  3. console.log(`arr has 10`, arr.some(s => s == 10))
  4. console.log(`arr has 1`, arr.some(s => s == 6))
英文:

You can use some method to check whether the data is existing in your array:

  1. if (!this.sQuestions.some(q =&gt; q.question == newQuestion)) 
  2. {
  3.   this.isQuestionExist = true;
  4. }
  5. else {
  6.   //save function
  7. }

An example:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

  1. let arr = [1, 2, 3, 4, 5];
  2. console.log(`arr has 1`, arr.some(s=&gt; s == 1))
  3. console.log(`arr has 10`, arr.some(s=&gt; s == 10))
  4. console.log(`arr has 1`, arr.some(s=&gt; s == 6))

<!-- end snippet -->

huangapple
  • 本文由 发表于 2020年1月3日 20:50:34
  • 转载请务必保留本文链接：https://go.coder-hub.com/59578964.html
  • arrays
  • javascript
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