TypeError and ReferenceError
July 31, 2019
How to create a TypeError
In general, a TypeError will be thrown when a value is not and can’t be converted to the expected type.
0() // TypeError: 0 is not a function
{ toString: null } + 1 // TypeError: Cannot convert object to primitive value
null.x // TypeError: Cannot read property 'x' of null
let Car = (name) => { this.name = name }
new Car() // TypeError: Car is not a constructor
for(let v of {}) { } // TypeError: {} is not iterableHow to create a ReferenceError
// ReferenceError: x is not defined
x + 1
x = 5
console.log(x)
/* ... */Only typeof operator can reference an undeclared variable and not throw an error (ReferenceError).
“Undeclared” is not the same as undefined, even though:
typeof x // 'undefined'