"echo" output different answer by sh and bash

Question

I ran my script using three ways and the output was different, could you explain to me why it works like that? Thanks!! Here is my script

#!/bin/bash
#Program:
#     This program shows "Hello World!" in your screen.
echo -e "Hello World! \a\n" 
exit 0

And if i run it by bash and ./ like bash sh01.sh the output is

Hello World!

However, if i use sh like sh sh01.sh it would be like

-e Hello World!

And Here is some other information

1. OS: Ubuntu 16.04.3
2. type sh -> dash

Answer 1

echo is not very portable (even Bash's echo may behave differently on different OSes which may use different default options when compiling Bash). You can use printf. According to posix:

It is not possible to use echo portably across all POSIX systems unless both -n (as the first argument) and escape sequences are omitted. The printf utility can be used portably to emulate any of the traditional behaviors of the echo utility [...]

---

I have this _echo() in my bashrc:

#
# _echo [-n] args...
#
function _echo()
{
    local eol='\n'

    if [[ $1 == '-n' ]]; then
        eol=''
        shift
    fi
    if [[ $1 == '--' ]]; then
        shift
    fi

    printf "%s$eol" "$*"
}