Angular - 如果属性存在则赋值

Question

Assign the value if the 'rowData' property exists. Can we do like below?

if(this.tableObj.hasOwnProperty('rowData')) {
  this.tableObj.rowData = this.defVal.rowData;
}

Getting the below error when I try this. that too inside the if condition.

Property 'rowData' does not exist on type '{}'.

UPDATED

@Input() tableObj: {};
defVal: {
    rowData: [1,2,3]
};
 
ngOnInit() {
}
 
reset() {
    if( this.tableObj.rowData !== undefined) {
        this.tableObj.rowData = this.defVal.rowData;
    }
}

Build Error

error TS2339: Property 'rowData' does not exist on type 'never'.

Answer 1

Yes you can. Few other ways to do this:

if ('rowData' in this.tableObj) {

}

Or

if (this.tableObj.rowData) {

}

And also the way you mentioned:

if (this.tableObj.hasOwnProperty('rowData')) {

}

Personally I like the first one the most, it explains itself pretty well in my opinion which helps readability.

EDIT:

I'm not entirely sure what you're trying to do, the rowData is an array, are you trying to see if a certain item in the array exists as a property in the object?

If you want to access a certain item in the array you need to specify the index, like this:

rowData[0]

0 is the first index of the array. Which in your case will be accessing the first value which is 1. Then to access the next one it'd be rowData[1] etc.

So your code should look something like this:

if (this.tableObj[this.rowData[0]] !== undefined) {
        this.tableObj[this.rowData[0]] = this.defVal.rowData;
}

Answer 2

To avoid the error you can try the below code in your if condition.

     if(this.tableObj && this.tableObj.rowData !== undefined){  
      this.tableObj.rowData = this.defVal.rowData;
      }