如何在包含前导零的JavaScript中增加字符串？

Question

I have string like:

MPG_0023

I want to find something like

MPG_0023 + 1

and I should get

MPG_0024

How to do that in JavaScript? It should take care that if there are no leading zeros, or one leading zero should still work like MPG23 should give MPG24 or MPG023 should give MPG024.

There should be no assumption that there is underscore or leading zeros, the only thing is that first part be any string or even no string and the number part may or may not have leading zeros and it is any kind of number so it should work for 0023 ( return 0024) or for gp031 ( return gp032) etc.

Answer 1

Here's a quick way without using regex.. as long as there's always a single underscore preceding the number and as long as the number is 4 digits, this will work.

 var n = 'MPG_0023'; var a = n.split('_'); var r = a[0]+'_'+(("0000"+(++a[1])).substr(-4)); console.log(r); 

Or if you do wanna do regex, the underscore won't matter.

 var n = "MPG_0099"; var r = n.replace(/(\\d+)/, (match)=>("0".repeat(4)+(++match)).substr(-4)); console.log(r); 

Answer 2

You can use the regular expressions to make the changes as shown in the following code

 var text = "MPG_0023"; var getPart = text.replace ( /[^\\d.]/g, '' ); // returns 0023 var num = parseInt(getPart); // returns 23 var newVal = num+1; // returns 24 var reg = new RegExp(num); // create dynamic regexp var newstring = text.replace ( reg, newVal ); // returns MPG_0024 console.log(num); console.log(newVal); console.log(reg); console.log(newstring); 

Answer 3

Using regex along with the function padStart

 function add(str, n) { return str.replace(/(\\d+)/, function(match) { var length = match.length; var newValue = Number(match) + n; return newValue.toString(10).padStart(length, "0"); }); } console.log(add("MPG_023", 101)); console.log(add("MPG_0023", 101)); console.log(add("MPG_0000023", 10001)); console.log(add("MPG_0100023", 10001)); 

Answer 4

You could cast to number, increment the value and cast back. Then check if you need leading zeros by looking at the length of the string.

Snippet below:

 let str = "MPG_0023", num = Number(str.substr(4)) + 1, newStr = String(num); function addLeading0(str) { return str.length === 2 ? '00' + str : (str.length === 3 ? '0' + str : str); } console.log("MPG_" + addLeading0(newStr)); 

Answer 5

Using regular expression you can do it like this.

var text1 = 'MPG_0023';
var text2 = 'MPG_23';

var regex = /(.*_[0]*)(\d*)/;

var match1 = regex.exec(text1);
var match2 = regex.exec(text2);

var newText1 = match1[1] + (Number(match1[2]) + 1);
var newText2 = match2[1] + (Number(match2[2]) + 1);

console.log(newText1);
console.log(newText2);

Answer 6

Increment and pad the same value ( comments inline )

 var prefix = "MPG_" var padDigit = 4; //number of total characters after prefix var value = "MPG_0023"; console.log("currentValue ", value); //method for padding var fnPad = (str, padDigit) => (Array(padDigit + 1).join("0") + str).slice(-padDigit); //method to get next value var fnGetNextCounterValue = (value) => { var num = value.substring(prefix.length); //extract num value ++num; //increment value return prefix + fnPad(num, padDigit); //prepend prefix after padding }; console.log( "Next", value = fnGetNextCounterValue(value) ); console.log( "Next", value = fnGetNextCounterValue(value) ); console.log( "Next", value = fnGetNextCounterValue(value) ); 

Answer 7

One way would e to split the string on the "_" character, increment the number and then add the zeros back to the number.

var testString = "MGP_0023";
var ary = testString.split("_");

var newNumber = Number(ary[1]) + 1;
var result = ary[0] + pad(newNumber);

// helper function to add zeros in front of the number
function pad(number) {
    var str = number.toString();
    while (str.length < 4) {
        str = '0' + str;
    }

    return str;
}