TypeError: setting getter-only property "x"

TypeError: Cannot set property x of #<Object> which has only a getter (V8-based) TypeError: '#x' was defined without a setter (V8-based) TypeError: setting getter-only property "x" (Firefox) TypeError: Attempted to assign to readonly property. (Safari) TypeError: Trying to access an undefined private setter (Safari) 

TypeError in strict mode only.

There is an attempt to set a new value to a property for which only a getter is specified. While this will be silently ignored in non-strict mode, it will throw a TypeError in strict mode. Classes are always in strict mode, so assigning to a getter-only private property always throws this error.

The example below shows how to set a getter for a property. It doesn't specify a setter, so a TypeError will be thrown upon trying to set the temperature property to 30. For more details see also the Object.defineProperty() page.

"use strict"; function Archiver() { const temperature = null; Object.defineProperty(this, "temperature", { get() { console.log("get!"); return temperature; }, }); } const arc = new Archiver(); arc.temperature; // 'get!' arc.temperature = 30; // TypeError: setting getter-only property "temperature" 

To fix this error, you will either need to remove the arc.temperature = 30 line, which attempts to set the temperature property, or you will need to implement a setter for it, for example like this:

"use strict"; function Archiver() { let temperature = null; const archive = []; Object.defineProperty(this, "temperature", { get() { console.log("get!"); return temperature; }, set(value) { temperature = value; archive.push({ val: temperature }); }, }); this.getArchive = function () { return archive; }; } const arc = new Archiver(); arc.temperature; // 'get!' arc.temperature = 11; arc.temperature = 13; arc.getArchive(); // [{ val: 11 }, { val: 13 }] 

• Object.defineProperty()
• Object.defineProperties()