var str1 ="Hello ";var str2 ="world!";var res = str1.concat(str2);// does not change the existing strings, but// returns a new string containing the text// of the joined strings.
//This method adds two or more strings and returns a new single string.let str1 =newString("This is string one");let str2 =newString("This is string two");let str3 = str1.concat(str2.toString());console.log("str1 + str2 : "+str3)output:
str1 + str2 :This is string oneThis is string two
let first_string ='I am a programmer, ';let second_string ='I am indisposable.';let what_i_said = first_string + second_string;console.log(what_i_said);/* OR
*/let tell_my_boss = first_string.concat(second_string);console.log(tell_my_boss);
//ES6 spread operator same as arr1.concat(arr2)var arr1 =['1','2','3']var arr2 =[4,5,6]
arr1 =[...arr1, arr2]//... removes the [ and ] // leavin only an instance of inside.output:['1','2','3',4,5,6]