typescript make a key equal to spcific strings code example

Example 1: typescriprt specify type of key

var stuff: { [key: string]: string; } = {};
stuff['a'] = ''; // ok
stuff['a'] = 4;  // error

// ... or, if you're using this a lot and don't want to type so much ...
interface StringMap { [key: string]: string; }
var stuff2: StringMap = { };
// same as above

Example 2: typescript string in object property

protected get ButtonClass(): object {
    const buttonClass = {
      'cursor-pointer hover:shadow focus:shadow': this.Enabled,
      'opacity-40 cursor-not-allowed': !this.Enabled,
      'whitespace-no-wrap': !this.LineBreaks
    }
    // The below allows you to define object properties based on a variable.
    // If you were to assign them in the snippet above, it would cause an error.
    buttonClass[`hover:${this.Color.FocusColorClass}`] = this.Enabled;
    buttonClass[`focus:${this.Color.FocusColorClass}`] = this.Enabled;
    buttonClass[`active:${this.Color.ActiveColorClass}`] = this.Enabled;
    return buttonClass;
  }