Target: Just the word's meaning, concatenate, which add some character or sting and return a new string.
Syntax: str.concat(str1 [, str2 [, str3 ... [, strN]]])
Special: 1.Not a type string, they are converted to string values before concatenating.
2. Actually, the assignment operator[ "+, +=] is faster than this, but this is a function method which can pass the arguments.
3. "".concat() // ""