Helper script for better Japanese line wrapping, using Kuromoji tokenizer library

kuromoji-helper.js

kuromoji.builder({ dicPath: "node_modules/kuromoji/dict/" }).build(function (err, tokenizer) {
    if(err)console.log(err);
    var textNodesUnder = function(node){ // http://stackoverflow.com/questions/10730309/find-all-text-nodes-in-html-page
      var all = [];
      for (node=node.firstChild;node;node=node.nextSibling){
        if (node.nodeType==3 && !/^\s+$/.test(node.data)) all.push(node);
        else all = all.concat(textNodesUnder(node));
      }
      return all;
    };
    function addSpanTags(){
        // This is the plan:
        // Get a list (preferably static..) of all text nodes in document
        // tokenize each of them
        // wrap each token in a SPAN tag styled with word-break: keep-all

        var textnodes = textNodesUnder(document.body);
        textnodes.forEach(function(textnode){
            if(textnode.parentNode.tagName in {'SCRIPT':1, 'STYLE':1}){
                return; // we would cause really funky effects if we messed with those nodes..
            }
            var words = tokenizer.tokenize(textnode.data);
            var indexes = [];
            words.forEach(function(wordData){
                if(wordData.surface_form.length > 2) { // do not bother with 1 char words
                    indexes.push([wordData.word_position - 1, wordData.word_position - 1 + wordData.surface_form.length]);
                }
            });
            // now we have all the indexes to split this text node at
            for(var newNode, span, after, i = indexes.length-1; i >= 0; i--) {
                console.log('will split ' + textnode.data + ' at ' + indexes[i][1]);
                if(indexes[i][1] != textnode.data.length){
                    textnode.splitText(indexes[i][1]); // chops off the remainder
                }
                newNode = textnode.splitText(indexes[i][0]); // chops off the string to wrap
                span = newNode.parentElement.insertBefore(document.createElement('span'), newNode);
                span.appendChild(newNode);
                span.className = 'avoid-wrap';
            }
        });

    }
    // tokenizer is ready
    document.readyState != 'complete' ? window.addEventListener('load', addSpanTags, false) : addSpanTags();
});