The Webix library offers predefined methods for number formatting. All of them are accessible via the i18n module and are mainly used during localization.
const string1 = webix.i18n.numberFormat("123.45");
const string2 = webix.i18n.intFormat("123.45")
const string3 = webix.i18n.priceFormat("123.45");
They will format data according to the rules stated in the current locale.
Applying locales within a component:
// datatable
{ header:"LongDate", width:170,  id:"start", format:webix.i18n.numberFormat }
 
// other components
template:function(obj) {return webix.i18n.numberFormat(obj.start); }
For more details dive into the Date and Number Localization article.
If you need to format a number with custom formatting rules, you can use the following methods of the Number class:
Here you need to specify rules right in a data component:
const string1 = webix.Number.format("-1236.45",{
    groupDelimiter:",",
    groupSize:3,
    decimalDelimiter:".",
    decimalSize:2,
    minusPosition:"after",
    minusSign:"-"
});
// -> 1,236.45-
Applying format within a component:
// datatable
{ header:"LongDate", width:170,  id:"votes", format:webix.Number.numToStr({
        groupDelimiter:"",
        groupSize:0,
        decimalDelimiter:",",
        decimalSize:5,
        minusPosition:"parentheses",
        minusSign:"()",
   }); 
}
 
// other components
template:function(obj) {
    return webix.Number.numToStr({
        groupDelimiter:"",
        groupSize:0,
        decimalDelimiter:",",
        decimalSize:5,
        minusPosition:"parentheses",
        minusSign:"()", 
    });
}
Related sample: Using Number Templates
You can also get the object with configuration options used for formatting:
const cfg = webix.Number.getConfig("1'111.00"); 
// ->{decimalSize: 2, groupSize: 3, decimalDelimiter: ".", groupDelimiter: "'", 
//    prefix: "", sufix: ""}
and define the format of a parsed value:
const num1 = webix.Number.parse("(10'009.00)", {
    decimalSize: 2, groupSize: 3, 
    decimalDelimiter: ".", groupDelimiter: "'",minusPosition:"parentheses",
    minusSign:"()",
});
// -> -10009