1var str1 = "Hello ";
2var str2 = "world!";
3var res = str1.concat(str2);
4console.log(res);
1const str1 = 'Hello';
2const str2 = 'World';
3
4console.log(str1 + str2);
5>> HelloWorld
6
7console.log(str1 + ' ' + str2);
8>> Hello World
1 var dest = new String("");
2 var src = new String("aze");
3 var ar = new Array();
4 ...
5 ar.push(src);
6 ar.push(src);
7 ...
8 dest = ar.join("");
1 var dest = new String("");
2 var src = new String("aze");
3 ...
4 dest += src + src + src + src + src;