Cannot assign to read only property 'x' of object '[object Object]'-CodePudding

After upgrading my project to Angular 12/TypeScript 4.3.5, I am getting the error above. Here is my code:

for (const metric of metrics) {
    if (!metric.focalThemeSubArea) {
        metric.focalThemeSubArea = metric.focalTheme;
    }
}

My Metric class is defined as follows:

export class ScaMetricGraphType {
    public focalTheme: string;
    public focalThemeSubArea: string;
    public isActive: boolean;
    public name: string;
}

I don't see anything that's read-only about focalThemeSubArea. While it's true that I declared metric as const in the loop, that shouldn't mean that its members become read-only. Unless something changed about TypeScript that I'm unaware of.

CodePudding user response：

You can not declare const inside the loop, instead it is better to use let.

CodePudding user response：

Use let instead of const inside for loop

CodePudding user response：

Try this instead, maybe this will work.

metric['focalThemeSubArea'] = metric['focalTheme']