Quick Answer

Fix invalid left-hand side assignments.

Understanding the Issue

This ReferenceError occurs when trying to assign a value to something that can't be assigned to. Common causes include assigning to function calls, literals, or incorrect destructuring patterns.

The Problem

This code demonstrates the issue:

Javascript Error 
5 = x; // Literal assignment
function() {} = 42; // Function assignment
[a, b] = {a: 1, b: 2}; // Wrong destructuring

The Solution

Here's the corrected code:

Javascript Fixed 
// Correct assignments
const x = 5;

// Function parameters
function setValue(val) {
    return val;
}

// Proper destructuring
const {a, b} = {a: 1, b: 2}; // Object destructuring
const [c, d] = [1, 2];       // Array destructuring

// Valid left-hand sides:
// - Variables (let, const, var)
// - Object properties
// - Array elements

Key Takeaways

Only valid references can be assignment targets.