TypeScript: Cannot read property 'push' of undefined in [null]

Question

Error: Cannot read property 'push' of undefined in [null].

class A implements OnInit {
    stringArr: string[];

    ngOnInit() {
        for(let i=0; i<4; i++) {
            this.stringArr.push("aaa");
        }
    }
}

question from:https://stackoverflow.com/questions/35689140/typescript-cannot-read-property-push-of-undefined-in-null

Answer 1

The array needs to be initialized:

stringArr = [];