<script>
var str = "this is a 'testing' by phpbasic";//hợp lệ
var str = 'this is a "testing" by phpbasic';//hợp lệ

var str = 'this is a 'testing' by phpbasic';// không hợp lệ
var str = 'this is a \'testing\' by phpbasic';// hợp lệ

var str = "this is a "testing" by phpbasic";//không hợp lệ
var str = "this is a \"testing\" by phpbasic";//hợp lệ

var str = "this is a testing
by phpbasic";// không hợp lệ
var str = "this is a testing\
by phpbasic";//  hợp lệ
</script>
</script>