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  • [Angular] ngClass conditional

    Using ngClass for conditional styling, here is the usage from the docs:

    /**
     * @ngModule CommonModule
     *
     * @usageNotes
     * ```
     *     <some-element [ngClass]="'first second'">...</some-element>
     *
     *     <some-element [ngClass]="['first', 'second']">...</some-element>
     *
     *     <some-element [ngClass]="{'first': true, 'second': true, 'third': false}">...</some-element>
     *
     *     <some-element [ngClass]="stringExp|arrayExp|objExp">...</some-element>
     *
     *     <some-element [ngClass]="{'class1 class2 class3' : true}">...</some-element>
     * ```
     *
     * @description
     *
     * Adds and removes CSS classes on an HTML element.
     *
     * The CSS classes are updated as follows, depending on the type of the expression evaluation:
     * - `string` - the CSS classes listed in the string (space delimited) are added,
     * - `Array` - the CSS classes declared as Array elements are added,
     * - `Object` - keys are CSS classes that get added when the expression given in the value
     *              evaluates to a truthy value, otherwise they are removed.
     *
     * @publicApi
     */

    It is also recommended when the conditional logics is complicated, we can using Function:

    <div [ngClass]="getCondClass(i)" *ngFor="let item of items as collection; index as i; first as isFirst; last as isLast; even as isEven; odd as isOdd;">
      {{i + 1}}: {{item}} -- {{collection}}
    </div>
      getCondClass (index) {
        if (index + 1 === 3) {
          // Using array to add 'third', 'very*important' classes
          return ['third', 'very-important'];
        }
    
        if (index === this.items.length - 1) {
          // Using string to add class
          return 'last';
        }
    
        if (index === 0) {
          // Using object to add class
          return {'first': true};
        }
      }
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  • 原文地址:https://www.cnblogs.com/Answer1215/p/10171855.html
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