<script>
window.addEventListener("DOMContentLoaded", function() {
    [].forEach.call( document.querySelectorAll("input[type='tel']"), function(input) {
    var keyCode;
    function mask(event) {
        event.keyCode && (keyCode = event.keyCode);
        var pos = this.selectionStart;
        if (pos < 3) event.preventDefault();
        if (pos === 3 && event.keyCode === 56) {
            event.preventDefault();
        }

        /*
        Берем значение инпута,
        удаляем все символы кроме цифр,
        если первая цифра 8, меняем ее на 7
        */
        var val = this.value.replace(/\D/g, "");
        if (val[0] === '8') val = '' + val.slice(1);

        var matrix = "+7 (___) ___ ____",
            i = 0,
            def = matrix.replace(/\D/g, ""),

            new_value = matrix.replace(/[_\d]/g, function(a) {
                return i < val.length ? val.charAt(i++) || def.charAt(i) : a
            });
        i = new_value.indexOf("_");
        if (i != -1) {
            i < 5 && (i = 3);
            new_value = new_value.slice(0, i)
        }
        var reg = matrix.substr(0, this.value.length).replace(/_+/g,
            function(a) {
                return "\\d{1," + a.length + "}"
            }).replace(/[+()]/g, "\\$&");
        reg = new RegExp("^" + reg + "$");
        if (!reg.test(this.value) || this.value.length < 5 || keyCode > 47 && keyCode < 58) this.value = new_value;
        if (event.type == "blur" && this.value.length < 17) {
            this.value = "";
        }
    }

    input.addEventListener("input", mask, false);
    input.addEventListener("focus", mask, false);
    input.addEventListener("blur", mask, false);
    input.addEventListener("keydown", mask, false)

  });
});

$( document ).ready(function() {
    let fields = document.querySelectorAll("input[type='tel']");

    for (let i = 0; i < fields.length; i++) {
        fields[i].addEventListener("paste", function(e) {
            var pastedText = undefined;

            if (window.clipboardData && window.clipboardData.getData) {
                pastedText = window.clipboardData.getData('Text');
            } else {
                var clipboardData = (e.originalEvent || e).clipboardData;
                if (clipboardData && clipboardData.getData) {
                    pastedText = clipboardData.getData('text/plain');
                }

                if(pastedText[0] === "8") {
                    e.target.value = "+7 " + pastedText.split("").slice(1).join("")
                } else {
                    e.target.value = pastedText
                }

                e.preventDefault();
                return false;
            }
        });
    }
});
</script>