just-left-pad/index.min.js

add characters to the left of a string such that its total length is n

module.exports=leftPad;var surrogatePairRegEx=/[\uD800-\uDBFF][\uDC00-\uDFFF]/g;function leftPad(str,length,padStr){if(typeof str!="string"||arguments.length>2&&typeof padStr!="string"||!(isFinite(length)&&length>=0&&Math.floor(length)===length)){throw Error("1st and 3rd args must be strings, 2nd arg must be a positive integer")}if(padStr==null||padStr==""){padStr=" "}var strLen=str.length-(str.match(surrogatePairRegEx)||[]).length;var padStrLen=padStr.length;var surrPairsInPad=(padStr.match(surrogatePairRegEx)||[]).length;if(surrPairsInPad&&padStrLen/surrPairsInPad!=2){throw Error("padding mixes regular characters and surrogate pairs")}if(!length||length<=strLen){return str}var padCount=Math.floor((length-strLen)/padStrLen);var padRemainder=(length-strLen)%padStrLen;if(surrPairsInPad){padCount=2*padCount;padRemainder=2*padRemainder}return(padRemainder?[padStr.slice(-padRemainder)]:[]).concat(new Array(padCount+1).join(padStr)).concat(str).join("")}