https://www.wedding-magazine.ru/wp-content/themes/wedding/assets/js-old/_4_number-input.js?ver=7.1.2

1// File#: _1_number-input
2// Usage: codyhouse.co/license
3(function() {
4    var InputNumber = function(element) {
5      this.element = element;
6      this.input = this.element.getElementsByClassName('js-number-input__value')[0];
7      this.min = parseFloat(this.input.getAttribute('min'));
8      this.max = parseFloat(this.input.getAttribute('max'));
9      this.step = parseFloat(this.input.getAttribute('step'));
10      if(isNaN(this.step)) this.step = 1;
11      this.precision = getStepPrecision(this.step);
12      initInputNumberEvents(this);
13    };
14  
15    function initInputNumberEvents(input) {
16      // listen to the click event on the custom increment buttons
17      input.element.addEventListener('click', function(event){ 
18        var increment = event.target.closest('.js-number-input__btn');
19        if(increment) {
20          event.preventDefault();
21          updateInputNumber(input, increment);
22        }
23      });
24  
25      // when input changes, make sure the new value is acceptable
26      input.input.addEventListener('focusout', function(event){
27        var value = parseFloat(input.input.value);
28        if( value < input.min ) value = input.min;
29        if( value > input.max ) value = input.max;
30        // check value is multiple of step
31        value = checkIsMultipleStep(input, value);
32        if( value != parseFloat(input.input.value)) input.input.value = value;
33  
34      });
35    };
36  
37    function getStepPrecision(step) {
38      // if step is a floating number, return its precision
39      return (step.toString().length - Math.floor(step).toString().length - 1);
40    };
41  
42    function updateInputNumber(input, btn) {
43      var value = ( Util.hasClass(btn, 'number-input__btn--plus') ) ? parseFloat(input.input.value) + input.step : parseFloat(input.input.value) - input.step;
44      if( input.precision > 0 ) value = value.toFixed(input.precision);
45      if( value < input.min ) value = input.min;
46      if( value > input.max ) value = input.max;
47      input.input.value = value;
48      input.input.dispatchEvent(new CustomEvent('change', {bubbles: true})); // trigger change event
49    };
50  
51    function checkIsMultipleStep(input, value) {
52      // check if the number inserted is a multiple of the step value
53      var remain = (value*10*input.precision)%(input.step*10*input.precision);
54      if( remain != 0) value = value - remain;
55      if( input.precision > 0 ) value = value.toFixed(input.precision);
56      return value;
57    };
58  
59    //initialize the InputNumber objects
60    var inputNumbers = document.getElementsByClassName('js-number-input');
61    if( inputNumbers.length > 0 ) {
62      for( var i = 0; i < inputNumbers.length; i++) {
63        (function(i){new InputNumber(inputNumbers[i]);})(i);
64      }
65    }
66  }());