Create mask for weight (kg)

You can use this plugin :

Create an external .js file with the name jQuery.weightMask.min.js and add the code below:

jQuery.fn.extend({maskWeight:function(t){window._maskData={selector:$(this),arr:[],insertCount:0,numberPressed:!1,options:{},defOptions:{integerDigits:3,decimalDigits:3,decimalMark:".",initVal:"",roundingZeros:!0,digitsCount:6,callBack:null,doFocus:!0},initializeOptions:function(t){if(this.options=$.extend(!0,this.defOptions),this.arr=[],this.insertCount=0,this.numberPressed=!1,t)for(var i in t)void 0!==t[i]&&null!==t[i]&&(this.options[i]=t[i]);0==this.options.decimalDigits&&(this.options.decimalMark="");var s=!1;if(""==this.options.initVal){if(this.options.roundingZeros)this.options.initVal+="0";else for(var n=0;n<this.options.integerDigits;n++)this.options.initVal+="0";this.options.initVal+=this.options.decimalMark;for(var n=0;n<this.options.decimalDigits;n++)this.options.initVal+="0"}else s=!0;this.options.digitsCount=this.options.integerDigits+this.options.decimalDigits,this.arr=[];for(var n=0;n<this.options.digitsCount;n++)this.arr.push("0");s&&parseInt(this.options.initVal)>0&&this.createInitialValueArr()},createInitialValueArr:function(){this.options.initVal=0==this.options.decimalDigits?parseInt(this.options.initVal):parseFloat(this.options.initVal.toString().replace(",",".")).toFixed(this.options.decimalDigits).replace(".",this.options.decimalMark);for(var t=this.options.initVal.toString().replace(".","").replace(",","").split(""),i=0;i<t.length;i++)this.insert(t[i])},insert:function(t){var i=this.mask(t);this.selector.val(i),this.setCartetOnEnd()},mask:function(t){"backspace"==t?this.insertCount>0&&(this.arr.pop(),this.arr.unshift("0"),this.insertCount--):this.insertCount<this.options.digitsCount&&(this.arr.shift(),this.arr.push(t.toString()),this.insertCount++);for(var i="",s=0;s<this.arr.length;s++)i+=this.arr[s];return i=this.reduce(i)},reduce:function(t){return 0==this.options.decimalDigits?this.options.roundingZeros?parseInt(t):t:this.options.roundingZeros?parseInt(t.substring(0,this.options.integerDigits))+this.options.decimalMark+t.substring(this.options.integerDigits,this.options.digitsCount):t.substring(0,this.options.integerDigits)+this.options.decimalMark+t.substring(this.options.integerDigits,this.options.digitsCount)},getNumber:function(t){return String.fromCharCode(t.keyCode||t.which)},setCartetOnEnd:function(){var t=this;setTimeout(function(){var i=t.selector.val().length;t.options.doFocus&&t.selector[0].focus(),t.selector[0].setSelectionRange(i,i)},1)},isNumberOrBackspace:function(t){return"backspace"==t?!0:parseInt(t)||0==parseInt(t)?!0:!1},init:function(){var t=this;this.selector.val(this.options.initVal),this.selector.on("click",function(i){t.setCartetOnEnd()});var i=navigator.userAgent.toLowerCase(),s=i.indexOf("android")>-1;s?(window._maskDataLastVal=this.selector.val(),this.selector[0].removeEventListener("input",window._maskDataAndroidMaskHandler,!0),setTimeout(function(){window._maskDataAndroidMaskHandler=function(i){if(i.preventDefault(),i.stopPropagation(),t.selector.val().length<window._maskDataLastVal.length)t.insert("backspace");else{var s=t.selector.val().charAt(t.selector.val().length-1);0==parseFloat(t.selector.val().replace(",","."))&&0==parseInt(s)?t.insert("backspace"):t.insert(s)}return window._maskDataLastVal=t.selector.val(),t.options.callBack&&t.options.callBack(),!1},t.selector[0].addEventListener("input",window._maskDataAndroidMaskHandler,!0)},0)):(this.selector.on("keydown",function(i){var s=i.keyCode||i.which;(8==s||46==s)&&(i.preventDefault(),i.stopPropagation(),t.insert("backspace")),t.options.callBack&&t.options.callBack()}),this.selector.on("keypress",function(i){i.keyCode||i.which;i.preventDefault(),i.stopPropagation();var s=t.getNumber(i);t.isNumberOrBackspace(s)&&(0==parseFloat(t.selector.val().replace(",","."))&&0==parseInt(s)?t.insert("backspace"):t.insert(s)),t.options.callBack&&t.options.callBack()}))}},window._maskData.initializeOptions(t),window._maskData.init()},removeMask:function(){window._maskData&&($(this).unbind(),window._maskData=null)}});

Then upload it to your page:

<script src="jQuery.weightMask.min.js"></script>

Then just apply to input as follows:

<script>
$('#mascara').maskWeight({
 integerDigits: 3, // número de dígitos inteiros
 decimalDigits: 2, // número de decimais
 decimalMark: ',' // separador
});
</script>

Example:

$('#mascara').maskWeight({
 integerDigits: 3,
 decimalDigits: 2,
 decimalMark: ','
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script><script>jQuery.fn.extend({maskWeight:function(t){window._maskData={selector:$(this),arr:[],insertCount:0,numberPressed:!1,options:{},defOptions:{integerDigits:3,decimalDigits:3,decimalMark:".",initVal:"",roundingZeros:!0,digitsCount:6,callBack:null,doFocus:!0},initializeOptions:function(t){if(this.options=$.extend(!0,this.defOptions),this.arr=[],this.insertCount=0,this.numberPressed=!1,t)for(var i in t)void 0!==t[i]&&null!==t[i]&&(this.options[i]=t[i]);0==this.options.decimalDigits&&(this.options.decimalMark="");var s=!1;if(""==this.options.initVal){if(this.options.roundingZeros)this.options.initVal+="0";else for(var n=0;n<this.options.integerDigits;n++)this.options.initVal+="0";this.options.initVal+=this.options.decimalMark;for(var n=0;n<this.options.decimalDigits;n++)this.options.initVal+="0"}else s=!0;this.options.digitsCount=this.options.integerDigits+this.options.decimalDigits,this.arr=[];for(var n=0;n<this.options.digitsCount;n++)this.arr.push("0");s&&parseInt(this.options.initVal)>0&&this.createInitialValueArr()},createInitialValueArr:function(){this.options.initVal=0==this.options.decimalDigits?parseInt(this.options.initVal):parseFloat(this.options.initVal.toString().replace(",",".")).toFixed(this.options.decimalDigits).replace(".",this.options.decimalMark);for(var t=this.options.initVal.toString().replace(".","").replace(",","").split(""),i=0;i<t.length;i++)this.insert(t[i])},insert:function(t){var i=this.mask(t);this.selector.val(i),this.setCartetOnEnd()},mask:function(t){"backspace"==t?this.insertCount>0&&(this.arr.pop(),this.arr.unshift("0"),this.insertCount--):this.insertCount<this.options.digitsCount&&(this.arr.shift(),this.arr.push(t.toString()),this.insertCount++);for(var i="",s=0;s<this.arr.length;s++)i+=this.arr[s];return i=this.reduce(i)},reduce:function(t){return 0==this.options.decimalDigits?this.options.roundingZeros?parseInt(t):t:this.options.roundingZeros?parseInt(t.substring(0,this.options.integerDigits))+this.options.decimalMark+t.substring(this.options.integerDigits,this.options.digitsCount):t.substring(0,this.options.integerDigits)+this.options.decimalMark+t.substring(this.options.integerDigits,this.options.digitsCount)},getNumber:function(t){return String.fromCharCode(t.keyCode||t.which)},setCartetOnEnd:function(){var t=this;setTimeout(function(){var i=t.selector.val().length;t.options.doFocus&&t.selector[0].focus(),t.selector[0].setSelectionRange(i,i)},1)},isNumberOrBackspace:function(t){return"backspace"==t?!0:parseInt(t)||0==parseInt(t)?!0:!1},init:function(){var t=this;this.selector.val(this.options.initVal),this.selector.on("click",function(i){t.setCartetOnEnd()});var i=navigator.userAgent.toLowerCase(),s=i.indexOf("android")>-1;s?(window._maskDataLastVal=this.selector.val(),this.selector[0].removeEventListener("input",window._maskDataAndroidMaskHandler,!0),setTimeout(function(){window._maskDataAndroidMaskHandler=function(i){if(i.preventDefault(),i.stopPropagation(),t.selector.val().length<window._maskDataLastVal.length)t.insert("backspace");else{var s=t.selector.val().charAt(t.selector.val().length-1);0==parseFloat(t.selector.val().replace(",","."))&&0==parseInt(s)?t.insert("backspace"):t.insert(s)}return window._maskDataLastVal=t.selector.val(),t.options.callBack&&t.options.callBack(),!1},t.selector[0].addEventListener("input",window._maskDataAndroidMaskHandler,!0)},0)):(this.selector.on("keydown",function(i){var s=i.keyCode||i.which;(8==s||46==s)&&(i.preventDefault(),i.stopPropagation(),t.insert("backspace")),t.options.callBack&&t.options.callBack()}),this.selector.on("keypress",function(i){i.keyCode||i.which;i.preventDefault(),i.stopPropagation();var s=t.getNumber(i);t.isNumberOrBackspace(s)&&(0==parseFloat(t.selector.val().replace(",","."))&&0==parseInt(s)?t.insert("backspace"):t.insert(s)),t.options.callBack&&t.options.callBack()}))}},window._maskData.initializeOptions(t),window._maskData.init()},removeMask:function(){window._maskData&&($(this).unbind(),window._maskData=null)}});
</script>

<input maxlength="6" type="text" id="mascara" />