In the book: "Secrets of the JavaScript Ninja" the author demonstrates this code:
<script type="text/javascript">
var outerValue = 'ninja'
function outerFunction() {
assert(outerValue, "I can see the ninja");
}
outerFunction();
</script>
The output is : I can see the ninja.
What is assert for? Why not just use console.log?
Javascript assert, The official explanation:
assert(value[, message])
The square brackets around message means the second parameter is optional.
javascript assert Tests if the first parameter (value) is truthy, if it is, it prints the second optional parameter to stdout.
assert(outerValue, "I can see the ninja");
Your variable outerValues has the string "ninja", javascript evaluates that for truthiness, it is truthy, so it outputs "I can see the ninja".
"assert" is a non-standard function. Although all the major browsers appear to have it in some form or another.
It writes a value to the console if the assertion is true. In this case, outerValue equates to a true value (e.g. not false). It is useful for testing and is not recommended for production use. The fact that it first evaluates a boolean value to determine if it should print the message makes it different from console.log.
