javascript - Operator '+' cannot be applied to types 'String' and 'String' in TypeScript -

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i new typescript trying play it. face wired problem. when try concatenate 2 string type using + operator it's give error

operator '+' cannot applied types 'string' , 'string'

my code snap is

var firstname: string = 'foo'; var lastname: string = 'bar'; var name = firstname + lastname;

if use string instead string or add ''it works fine. checked, within javascript can use + on 2 string object why it's show error in typescript ? bug or feature ? missing something. detail explanation appreciated.

string not same string. use string unless really, know you're to.

the upper-case name string refers boxed version of primitive string. these should avoided wherever possible -- don't behave normal strings in subtle , unexpected ways (for example typeof new string('hello') "object", not "string").


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