According to https://github.com/jerryscript-project/jerryscript/blob/badfdf4dba1fa0a15bd78163c1713ada5e65cd22/jerry-core/lit/lit-magic-strings.c#L44 We can use lit_magic_strings[id] - lit_magic_strings[id+1] to calcuate the length of `lit_magic_strings[id]`, without the need of strlen.