Const defined variables and for of and for in in JS

1.const The declaration is expressed as a static variable , Attempting to modify will result in an error , And the variables must be initialized when defining .

2. This variable is not allowed to be declared repeatedly

3. His scope is also a block

4.congst The declaration of only applies to variables , If you define an object , Can't change value

5. Out-of-service const Declare iteration variables , Because the iteration variable will increase automatically . But you can state that it won't be modified for Loop variable . This is right for-in and for-of Cycles are particularly meaningful

for-of and for-in difference

1.for-of Will traverse the values of the array , and for-in Only the subscripts of the array will be traversed .

2.for-of It doesn't traverse the prototype chain , and for-in Will traverse the prototype chain .

3.for-of Suitable for traversing arrays or strings , It is not suitable for traversing objects .