角度2: 如何写一个 for 循环，而不是 foreach 循环

使用角度2，我想在一个模板中多次复制一条线。在对象上迭代很容易，*ngFor="let object of objects"。但是，我想运行一个简单的 for循环，而不是 foreach循环。类似(伪代码)的东西:

{for i = 0; i < 5; i++}
<li>Something</li>
{endfor}

我要怎么做？

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You could dynamically generate an array of however time you wanted to render <li>Something</li>, and then do ngFor over that collection. Also you could take use of index of current element too.

Markup

<ul>
<li *ngFor="let item of createRange(5); let currentElementIndex=index+1">
\{\{currentElementIndex}} Something
</li>
</ul>

Code

createRange(number){
// return new Array(number);
return new Array(number).fill(0)
.map((n, index) => index + 1);
}

Demo Here

Under the hood angular de-sugared this *ngFor syntax to ng-template version.

<ul>
<ng-template ngFor let-item [ngForOf]="createRange(5)" let-currentElementIndex="(index + 1)" [ngForTrackBy]="trackByFn">
\{\{currentElementIndex}} Something
</ng-template>
</ul>
小开

You can do both in one if you use index

<div *ngFor="let item of items; let myIndex = index>
\{\{myIndex}}
</div>

With this you can get the best of both worlds.

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最佳答案

You can instantiate an empty array with a given number of entries if you pass an int to the Array constructor and then iterate over it via ngFor.

In your component code :

export class ForLoop {
fakeArray = new Array(12);
}

In your template :

<ul>
<li *ngFor="let a of fakeArray; let index = index">Something \{\{ index }}</li>
</ul>

The index properties give you the iteration number.

Live version

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Depending on the length of the wanted loop, maybe even a more "template-driven" solution:

<ul>
<li *ngFor="let index of [0,1,2,3,4,5]">
\{\{ index }}
</li>
</ul>
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The better way to do this is creating a fake array in component:

In Component: 

fakeArray = new Array(12);

InTemplate:

<ng-container *ngFor = "let n of fakeArray">
MyCONTENT
</ng-container>

Plunkr here

小开

you can use _.range([optional] start, end). It creates a new Minified list containing an interval of numbers from start (inclusive) until the end (exclusive). Here I am using lodash.js ._range() method.

Example:

CODE

var dayOfMonth = _.range(1,32);  // It creates a new list from 1 to 31.

//HTML Now, you can use it in For loop

<div *ngFor="let day of dayOfMonth">\{\{day}}</div>
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If you want to use the object of ith term and input it to another component in each iteration then:

<table class="table table-striped table-hover">
<tr>
<th> Blogs </th>
</tr>
<tr *ngFor="let blogEl of blogs">
<app-blog-item [blog]="blogEl"> </app-blog-item>
</tr>
</table>
小开 
   queNumMin = 23;
queNumMax= 26;
result = 0;
for (let index = this.queNumMin; index <= this.queNumMax; index++) {
this.result = index
console.log( this.result);
}

Range min and max number

小开

If you want duplicate lines multiple time.

You can simply do :-

declare in .ts file

public repeater = "<li>Something</li>";

Then use following to print it .html file.

\{\{repeater.repeat(5)}}
小开

for Example let say you have an array called myArray if you want to iterate over it

<ul>
<li *ngFor="let array of myArray; let i = index">\{\{i}} \{\{array}}</li>
</ul>
小开

The best answer for this question I have found here

You need to create an attribute inside your class and reference it to Array object:

export class SomeComponent {
Arr = Array; //Array type captured in a variable
num:number = 20;
}

And inside your HTML you can use:

<ul id="next-pages">
<li class="line" *ngFor="let _ of Arr(10)">&nbsp;</li>
</ul>

提交答案