angularjs-track-by | 易学教程

ng-init is not calling second time when track by $index used

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问题 html: <table> <tbody> <tr ng-repeat="row in Rows track by $index" ng-init="initUserDecision(row,$index)" > <td>{{employeeName}}</td> </tr> </table> <button id="change"/> controller: $scope.initUserDecision = function(row,index){ $scope.employeeName=row["name"]; } $scope.rows=[{id:1,name:'siva'},{id:2,name:'ram'}] //changing $scope.rows in button click event and used $scope.$apply as well angular.element(document).on("click", "#change", function () { $scope.rows=[{id:1,name:'ravi'},{id:2,name:

ng-repeat with track by over multiple properties

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问题 I have a problem with angular ng-repeat directive. Currently I work on some project where from the API I get a list of items (some times it could be 1k items) and this list should be refreshed every 5 seconds (it is monitoring related project). When the list length is a little bigger the website while re-rendering DOM could "slow". It comes out that angular regenerate the whole DOM (but 95% of item are the same ! ) One of the possible approach is to set "track by" expression for example to

What is “track by” in AngularJS and how does it work?

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问题 I don't really understand how track by works and what it does. My main goal is to use it with ng-repeat to add some precision. 回答1: Using track by to track strings & duplicate values Normally ng-repeat tracks each item by the item itself. For the given array objs = [ 'one', 'one', 2, 'five', 'string', 'foo'] , ng-repeat attempts to track changes by each obj in the ng-repeat="obj in objs" . The problem is that we have duplicate values and angular will throw an error. One way to solve that is

How to use trackBy with ngFor

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问题 I can't really understand what I should return from trackBy . Based on examples I've seen on the web, I should return the value of some property on the object. Is it correct? Why do I get index as a parameter? For example, in the following case: constructor() { window.setInterval(() => this.users = [ {name: 'user1', score: Math.random()}, {name: 'user2', score: Math.random()}], 1000); } userByName(index, user) { return user.name; } ... <div *ngFor="let user of users; trackBy:userByName">{

deleting an element in ng-repeat with orderBy and track by is failing

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问题 Here is the code <tr ng-repeat="collection in collections | orderBy:'-modifiedDate' track by $index" ng-init="listIndex = $index"> If I remove orderBy:'-modifiedDate' , the deletion on a specific element is working great. However, I need the collection/array to be rendered in sorted way that's why I have orderBy. If I don't delete the orderBy:'-modifiedDate' from the code and I delete a random element say on position 7, the element that gets deleted is the very last always. I had to use ng

Angular 4 - Reactive Forms - select item in a list from object not referenced in this list - trackby issue?

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问题 I am converting Angular 1.6 code to Angular 4 and I have an issue with a list of elements. The code in Angular 1.6 is: <select ng-model="$ctrl.level" ng-options="item as item.label for item in $ctrl.referentiel.levels | orderBy : 'index' track by item.id" id="childLevel" name="childLevel" class="size-xl" > <option value="">Select</option> </select> The object level is not referenced in my list because this list is loaded using the object referentiel.levels. But the matching between the

What is “track by” in AngularJS and how does it work?

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I don't really understand how track by works and what it does. My main goal is to use it with ng-repeat to add some precision. Using track by to track strings & duplicate values Normally ng-repeat tracks each item by the item itself. For the given array objs = [ 'one', 'one', 2, 'five', 'string', 'foo'] , ng-repeat attempts to track changes by each obj in the ng-repeat="obj in objs" . The problem is that we have duplicate values and angular will throw an error. One way to solve that is to have angular track the objects by other means. For strings, track by $index is a good solution as you

How to use trackBy with ngFor

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I can't really understand what I should return from trackBy . Based on examples I've seen on the web, I should return the value of some property on the object. Is it correct? Why do I get index as a parameter? For example, in the following case: constructor() { window.setInterval(() => this.users = [ {name: 'user1', score: Math.random()}, {name: 'user2', score: Math.random()}], 1000); } userByName(index, user) { return user.name; } ... <div *ngFor="let user of users; trackBy:userByName">{{user.name}} -> {{user.score}}</div> The objects shown in template are still updated despite the name being

how to use track by inside ngFor angular 2

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tried every syntax i can guess couldnt make it works !  <ion-card *ngFor="#post of posts"> {{post|json}} </ion-card>  <ion-card *ngFor="#post of posts track by post.id"> {{post|json}} </ion-card>  <ion-card *ngFor="#post of posts;trackBy:post.id"> {{post|json}} </ion-card>  <ion-card *ngFor="#post of posts;trackBy:posts[index].id"> {{post|json}} </ion-card>  <ion-card *ngFor="

how to use track by inside ngFor angular 2

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问题 tried every syntax i can guess couldnt make it works !  <ion-card *ngFor=\"#post of posts\"> {{post|json}} </ion-card>  <ion-card *ngFor=\"#post of posts track by post.id\"> {{post|json}} </ion-card>  <ion-card *ngFor=\"#post of posts;trackBy:post.id\"> {{post|json}} </ion-card>  <ion-card *ngFor=\"#post of posts