JS solves the problem of Cannot set properties of undefined

TypeError: Cannot set properties of undefined
Type error: Undefined property cannot be set

Problem analysis

The current object or array is undefined, but is used to refer to attributes or indexes.

For example, the following two situations

const value = undefined
  // TypeError: Cannot read properties of undefined (reading 'a')
value[0]  // TypeError: Cannot read properties of undefined (reading '0')

Or the current value is not undefined as we explicitly declared, but is undefined after the operation, and then we use it

const value = {}
 // TypeError: Cannot read properties of undefined (reading 'b')
  // undefined

Solution

The problem is clear, the solution is to directly apply the object without undefined. You can use the following methods to solve the error problem

const value = undefined
//Solution 1: if conditionif（value）{
  value = {}
	
}
// Solution 2:? Operatorvalue?.a
// Solution 3: || operatorconst preValue = value || {}

This is the end of this article about how JS solves Cannot set properties of undefined. For more related js solution, please search for my previous articles or continue to browse the related articles below. I hope everyone will support me in the future!