What does the || (logical OR, double vertical line) expression do as a stand-alone statement?

The code below makes sense individually, but i do not get how it all works when it is combined into one statement like shown below.

The line i have trouble understanding is "discard.test(word) || (......" What is the or || operators doing in this statement?

words.forEach(function(word) {
  discard.test(word) ||
    (word = word.replace(punctuation, ""),
      stopWords.test(word.toLowerCase()) ||
    (word = word.substr(0, maxLength),
      tag_index[word.toLowerCase()] = word,
      tags[word = word.toLowerCase()] = (tags[word] || 0) + 1));
});

Basically it is this, a bit rectified.

words.forEach(function(word) {
    if (!discard.test(word)) {
        word = word.replace(punctuation, "");
        if (!stopWords.test(word.toLowerCase()) {
            word = word.substr(0, maxLength);
            tag_index[word.toLowerCase()] = word;
            word = word.toLowerCase();
            tags[word] = (tags[word] || 0) + 1);
        }
    }
});

It's a short writing for

if (!condition) {
}