Javascript search string using array

Question

I am trying to search the text of a body of a webpage against a list of predefined words in an array. Then record how many instances of each word appeared.

<script>
var str = document.body.innerText;
var array = [];
array[0] = "Statement";
array[1] = "Documents"; 
var regexp = new RegExp( '\\b' + array.join('\\b|\\b') + '\\b').test(str);
document.write(regexp)
</script>

That one is only returning true or false. Or is there a way to make this one work?

var str = document.body.innerText;
var n = str.match(use array here)
document.write(n)

Answer 1

Try this

n = str.match(new RegExp('\\b(' + arr.join('|') + ')\\b', 'ig')) || []).length;

1. make a dynamic Regex with i and g flag

    new RegExp('\\\\b(' + arr.join('|') + ')\\\\b', 'ig') 

2. define an empty array as fallback

    str.match(regex) || [] 

3. return the length of the results array or the fallback array

    str.match(new RegExp('\\\\b(' + arr.join('|') + ')\\\\b', 'ig')) || []).length;