ES6 const usage, es6const usage

ES6 const usage, es6const usage

1,ConstDeclare a read-only constant. Once declared, the constant value cannot be changed.

2,ConstScope andLetThe command is the same: onlyBlock-level scope.

3,ConstThe constants declared by the command are not upgraded.And can only be used after the declared position.

4. ES6:VarCommands andFunctionThe global variable declared by the command is still the attribute of the top-level object,LetCommands,ConstCommands,ClassGlobal variables declared by the command,Does not belong to the attribute of the top-level object. That is to say, starting from ES6, global variables will gradually be decoupled from the attributes of top-level objects.

Let B = 1; // console output undefinedwindow. B