Cannot read property 'push' of undefined angular

Question

I'm trying to push to the end of array a new value when onSubmit event is raised. My code looks like this:

  accounts: Account[] = [];
  feeAccount: Account = new Account();

  onSubmit(f: FormsModule) {
    console.log('Fee account -> ' + this.feeAccount);
    this.accounts.push(this.feeAccount);
  }

The problem is that I'm getting an error: Cannot read property 'push' of undefined. in spite of correct value logged just before it tries to push. What could be wrong here? I believe it is defined if it is logged correctly in the same method, or am I getting something wrong?

Check that you're not accidentally mutating accounts, it appears to be correctly defined in the code above but if you're getting that error it suggests that it can't access this.accounts suggesting it's been changed to undefined from an empty array. — Levidps
– Levidps, Commented Apr 24, 2020 at 11:33

Derviş Kayımbaşıoğlu · Accepted Answer · 2020-04-24 11:33:34Z

1

It seems that, in somewhere in your code, you are assigning another type to accounts variable or mutating it acciendally which is obviously not array anymore

add console.log to debug accounts object on submit action

console.log(this.accounts);
console.log(typeof this.accounts);

will give you clear idea

answered Apr 24, 2020 at 11:33

Derviş Kayımbaşıoğlu

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4 Comments

Levidps Over a year ago

The type wouldn't cause the error as JS doesn't actually have type checking when it's run. The error is caused b/c somewhere the value of this.accounts has been changed, not the type :)

Derviş Kayımbaşıoğlu Over a year ago

I am not talking about type checking. but the type is actually changing from array to something else. Author is defined it as array but it is not anymore. it is something else like null, undefined, object or vs

developer1 Over a year ago

@DervişKayımbaşıoğlu it is undefined, but shouldn't it be undefined because now I'm trying to define it?

Levidps Over a year ago

@DervişKayımbaşıoğlu sounds like a minor variance of semantics with value vs type.

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