Dynamically Add CSS Classes to Item Rows

SlickGrid is very flexible and it allows you to change or add CSS Class(es) dynamically (or on page load) by changing it's Item Metadata (see SlickGrid Wiki - Item Metadata). There is also a Stack Overflow answer, which this code below is based from.

Demo

Demo Page / Demo Component

Dynamically Change CSS Classes

View

<button class="btn btn-sm btn-default" (click)="changeDurationBackgroundColor()">Highlight Rows with Duration over 50</button>

<angular-slickgrid gridId="grid2" 
  [columnDefinitions]="columnDefinitions" 
  [gridOptions]="gridOptions" 
  [dataset]="dataset"
  (onAngularGridCreated)="angularGridReady($event.detail)">
</angular-slickgrid>

Component

// VERY IMPORTANT
// changing CSS Styles only seems to work with Encapsulation set to None
@Component({
  styles: ['.duration-bg { background-color: #e9d4f1 !important }'],
  encapsulation: ViewEncapsulation.None,
  templateUrl: './grid-additem.component.html'
})
export class Example {
  // get the SlickGrid Grid & DataView object references
  angularGridReady(angularGrid: AngularGridInstance) {
    this.angularGrid = angularGrid;
    this.dataView = angularGrid.dataView;
    this.grid = angularGrid.slickGrid;
  }

  /** 
   * Change the Duration Rows Background Color 
   * You need to get previous SlickGrid DataView Item Metadata and override it
   */
  changeDurationBackgroundColor() {
    this.dataView.getItemMetadata = this.updateItemMetadataForDurationOver50(this.dataView.getItemMetadata);

    // also re-render the grid for the styling to be applied right away
    this.grid.invalidate();
    this.grid.render();
  }

  /**
   * Override the SlickGrid Item Metadata, we will add a CSS class on all rows with a Duration over 50
   * For more info, you can see this SO https://stackoverflow.com/a/19985148/1212166
   */
  updateItemMetadataForDurationOver50(previousItemMetadata: any) {
    const newCssClass = 'duration-bg';

    return (rowNumber: number) => {
      const item = this.dataView.getItem(rowNumber);
      let meta = {
        cssClasses: ''
      };
      if (typeof previousItemMetadata === 'object') {
        meta = previousItemMetadata(rowNumber);
      }

      // our condition to check Duration over 50
      if (meta && item && item.duration) {
        const duration = +item.duration; // convert to number
        if (duration > 50) {
          meta.cssClasses = (meta.cssClasses || '') + ' ' + newCssClass;
        }
      }

      return meta;
    };
  }
}

On Page Load

Or if you want to apply the styling right after the page load

Component

export class Example {

  angularGridReady(angularGrid: AngularGridInstance) {
    this.angularGrid = angularGrid;
    this.dataView = angularGrid.dataView;
    this.grid = angularGrid.slickGrid;

    // if you want to change background color of Duration over 50 right after page load,
    // you would put the code here, also make sure to re-render the grid for the styling to be applied right away
    this.dataView.getItemMetadata = this.updateItemMetadataForDurationOver50(this.dataView.getItemMetadata);
    this.grid.invalidate();
    this.grid.render();
  }

  /**
   * Change the SlickGrid Item Metadata, we will add a CSS class on all rows with a Duration over 50
   * For more info, you can see this SO https://stackoverflow.com/a/19985148/1212166
   */
  updateItemMetadataForDurationOver50(previousItemMetadata: any) {
    const newCssClass = 'duration-bg';

    return (rowNumber: number) => {
      const item = this.dataView.getItem(rowNumber);
      let meta = {
        cssClasses: ''
      };
      if (typeof previousItemMetadata === 'object') {
        meta = previousItemMetadata(rowNumber);
      }

      if (meta && item && item.duration) {
        const duration = +item.duration; // convert to number
        if (duration > 50) {
          meta.cssClasses = (meta.cssClasses || '') + ' ' + newCssClass;
        }
      }

      return meta;
    };
  }
}