XML Minifier in Javascript / NodeJS

minify_xml.js

/**
 * A tool to minify XML strings
 * This code was borrowed and adapted from vkbeautify xml
 * https://github.com/vkiryukhin/vkBeautify/blob/master/vkbeautify.js
 */
function XMLMinifier () {
    function xml(text, step = "\t") {
        const ar = text
            .replace(/>\s{0,}</g, "><")
            .replace(/</g, "~::~<")
            .replace(/\s*xmlns\:/g, "~::~xmlns:")
            .replace(/\s*xmlns\=/g, "~::~xmlns=")
            .split("~::~")
        let len = ar.length
        let inComment = false
        let deep = 0
        let str = ""
        let ix = 0
        let shift = createShiftArr(step)

        for (ix = 0; ix < len; ix++) {
            // start comment or <![CDATA[...]]> or <!DOCTYPE //
            if (ar[ix].search(/<!/) > -1) {
                str += shift[deep] + ar[ix]
                inComment = true
                // end comment  or <![CDATA[...]]> //
                if (
                    ar[ix].search(/-->/) > -1 ||
                    ar[ix].search(/\]>/) > -1 ||
                    ar[ix].search(/!DOCTYPE/) > -1
                ) {
                    inComment = false
                }
            }
            // end comment  or <![CDATA[...]]> //
            else if (ar[ix].search(/-->/) > -1 || ar[ix].search(/\]>/) > -1) {
                str += ar[ix]
                inComment = false
            }
            // <elm></elm> //
            else if (
                /^<\w/.exec(ar[ix - 1]) &&
                /^<\/\w/.exec(ar[ix]) &&
                /^<[\w:\-\.\,]+/.exec(ar[ix - 1]) ==
                    /^<\/[\w:\-\.\,]+/.exec(ar[ix])[0].replace("/", "")
            ) {
                str += ar[ix]
                if (!inComment) deep--
            }
            // <elm> //
            else if (
                ar[ix].search(/<\w/) > -1 &&
                ar[ix].search(/<\//) == -1 &&
                ar[ix].search(/\/>/) == -1
            ) {
                str = !inComment ? (str += shift[deep++] + ar[ix]) : (str += ar[ix])
            }
            // <elm>...</elm> //
            else if (ar[ix].search(/<\w/) > -1 && ar[ix].search(/<\//) > -1) {
                str = !inComment ? (str += shift[deep] + ar[ix]) : (str += ar[ix])
            }
            // </elm> //
            else if (ar[ix].search(/<\//) > -1) {
                str = !inComment ? (str += shift[--deep] + ar[ix]) : (str += ar[ix])
            }
            // <elm/> //
            else if (ar[ix].search(/\/>/) > -1) {
                str = !inComment ? (str += shift[deep] + ar[ix]) : (str += ar[ix])
            }
            // <? xml ... ?> //
            else if (ar[ix].search(/<\?/) > -1) {
                str += shift[deep] + ar[ix]
            }
            // xmlns //
            else if (ar[ix].search(/xmlns\:/) > -1 || ar[ix].search(/xmlns\=/) > -1) {
                str += shift[deep] + ar[ix]
            } else {
                str += ar[ix]
            }
        }

        return str[0] == "\n" ? str.slice(1) : str
    }

    function createShiftArr(step) {
        let space = "    "

        if (isNaN(parseInt(step))) {
            // argument is string
            space = step
        } else {
            // argument is integer
            switch (step) {
                case 1:
                    space = " "
                    break
                case 2:
                    space = "  "
                    break
                case 3:
                    space = "   "
                    break
                case 4:
                    space = "    "
                    break
                case 5:
                    space = "     "
                    break
                case 6:
                    space = "      "
                    break
                case 7:
                    space = "       "
                    break
                case 8:
                    space = "        "
                    break
                case 9:
                    space = "         "
                    break
                case 10:
                    space = "          "
                    break
                case 11:
                    space = "           "
                    break
                case 12:
                    space = "            "
                    break
            }
        }

        const shift = ["\n"] // array of shifts

        for (ix = 0; ix < 100; ix++) {
            shift.push(shift[ix] + space)
        }

        return shift
    }

    function minifyXML(text, preserveComments) {
        let xmlStr = xml(text)

        return preserveComments
            ? xmlStr
            : xmlStr
                  .replace(/[\r\n\t]/g, " ")
                  .replace(/\<![ \r\n\t]*(--([^\-]|[\r\n]|-[^\-])*--[ \r\n\t]*)\>/g, "")
                  .replace(/[ \r\n\t]{1,}xmlns/g, " xmlns")
                  .replace(/>\s{0,}</g, "><")
                  .trim()
    }

    return {
        /**
         * Minify a XML string
         *
         * @param {String} xmlStr 
         * @param {Boolean} preserveComments 
         */
        minify(xmlStr, preserveComments = false) {
            return minifyXML(xmlStr, preserveComments)
        }
    }
}

module.exports = {
    XMLMinifier
}

Usage:

const { XMLMinifier } = require('./xml_minifier')
const minifier = XMLMinifier()

minifier.minify(`
<?xml version="1.0" encoding="UTF-8"?>
<Transaction TimeStamp="2019-09-23T01:00:00" ID="7a123456-123a0bcdefg1-2410921318">
    <Success />
    <ResponseTime ProcessTime="0.157" ProcessTimeUnit="Seconds" />
</Transaction>`
)

// <?xml version="1.0" encoding="UTF-8"?><Transaction TimeStamp="2019-09-23T01:00:00" ID="7a123456-123a0bcdefg1-2410921318"><Success /><ResponseTime ProcessTime="0.157" ProcessTimeUnit="Seconds" /></Transaction>