Angular ForEach in Angular4/Typescript?

in angular4 foreach like that. try this.

 selectChildren(data, $event) {
      let parentChecked = data.checked;
       this.hierarchicalData.forEach(obj => {
          obj.forEach(childObj=> {
            value.checked = parentChecked;
         });
      });
    }

you can try typescript's For :

selectChildren(data , $event){
   let parentChecked : boolean = data.checked;
   for(let o of this.hierarchicalData){
      for(let child of o){
         child.checked = parentChecked;
      }
   }
}

arrayData.forEach((key : any, val: any) => {
                        key['index'] = val + 1;

                        arrayData2.forEach((keys : any, vals :any) => {
                            if (key.group_id == keys.id) {
                                key.group_name = keys.group_name;
                            }
                        })
                    })