typescript, when declare variable and object inside class method, why only primitive type need...

For the following example

export class AppComponent implements OnInit {
driveTypes: string[];
vehicleTypes: string[];
vehicle: Vehicle;
test2:string;
testObj2 :{key2:'value2'};

method1(){
let test1:string;
let test2 = 'abc';
test3:string; // 'string' only refers to a type, but is being used as a value here.(2693)
test4 = 'def'; // Cannot find name 'test4'. Did you mean 'test1'?(2552)
testObj : {key1:'value1'};
let testObj2 : {key3:'value3'};
}


Inside method1(), why test3, test4 has error and must use let keyword like

let test1:string;
let test2 = 'abc';


but

testObj : {key1:'value1'};


has no any error?

Continue reading...