Array is undefined: ERROR TypeError: Cannot read property 'push' of undefined

Question

I have an array that is not defined and my drop down is breaking however if I console.log the array I can see the values.

Here is my ts code

This fires onInit

rolesArr: SelectItem[];

let obj = {  1: "System Admin",  2: "Internal Account Manager",  3: "CAT Manager",
4: "HR Admin",  5: "HR Manager",  6: "HR Recruiter",  7: "Candidate",
8: "Operations administrator"},
result = Object.entries(obj).reduce((a, [label, value]) => 
a.concat({label, value}), []);
    this.rolesArr.push(...result);

Here is my HTML

<div class="ui-g-6 ui-sm-12">
  <div class="input-container">
    <label for="role">Role*</label>
    <p-dropdown [options]="rolesArr"
        formControlName="role" id="role" placeholder="Please select">
    </p-dropdown>
  </div>
</div>

Possible duplicate of Typescript undefined is not an object when pushing to array — John Montgomery
– John Montgomery, Commented Apr 17, 2019 at 17:41

dev-dan · Accepted Answer · 2019-04-17 17:40:18Z

1

You need to initialise the array as you have only declared it with a type. This means the array cannot be pushed to as it does not yet exist. Try declaring it with the correct type as an empty array.

public rolesArr: SelectItem[] = [];

answered Apr 17, 2019 at 17:40

dev-dan

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Comments

Dmitry Grinko · Accepted Answer · 2019-04-17 22:30:55Z

0

Try to add ngIf

<div class="ui-g-6 ui-sm-12" *ngIf="rolesArr.length">
  <div class="input-container">
    <label for="role">Role*</label>
    <p-dropdown [options]="rolesArr" formControlName="role" id="role" placeholder="Please select"></p-dropdown>
  </div>
</div>

and you should set a default value for array

rolesArr: SelectItem[] = [];

edited Apr 17, 2019 at 22:30

answered Apr 17, 2019 at 17:41

Dmitry Grinko

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