1.限制输入框只能填写数字
大家都知道，在输入框限制只能输入数字用JS的来判断要考虑的情况比较多，比如中文切换，复制粘贴限制，用reactJS来实现很简单

var _val = ""; /*保存上次的值*/
var R_header = React.createClass({
    getInitialState:function(){
        return {info:""};
    },
    changeVal:function(e){
        var val = e.target.value;
        if(isNaN(val)){
            val = _val;
            this.setState({"info":"只能输入数字!"});
            setTimeout(function(){
                this.setState({"info":""});
            }.bind(this),1000);
        }else{
            _val = val; 
        }
        this.setState({"val":val});
    },
    render:function(){
        return (
            <div>
                <input type="text" defaultValue="" name="title" value={this.state.val} onChange={this.changeVal} />
                <label for="title">{this.state.info}</label>
            </div>
        );
    }
});

2.限制输入框的字数

changeVal:function(e){
        var val = e.target.value;
        var length = val.length;
        this.setState({"i_val":val.substring(0,10)});
        if(length > 10){
            this.setState({"info":"不能输入超过10个字!"});
            setTimeout(function(){
                this.setState({"info":""});
            }.bind(this),1000);
        }else{
            this.setState({"info":""});
        }
    },
    render:function(){
        return (
            <div>
                <input type="text" defaultValue="" name="title" value={this.state.i_val} onChange={this.changeVal} />
                <label for="title">{this.state.info}</label>
            </div>
        );
    }

3.即时显示还可以输入多少个字

var R_header = React.createClass({
    getInitialState:function(){
        return {info:10};
    },
    changeVal:function(e){
        var val = e.target.value;
        var length = val.length;
        this.setState({"i_val":val.substring(0,10)});
        length < 11?this.setState({"info":(10-length)}):"";
    },
    render:function(){
        return (
            <div>
                <input type="text" defaultValue="" name="title" value={this.state.i_val} onChange={this.changeVal} />
                <label for="title">您还可以输入{this.state.info}个字</label>
            </div>
        );
    }
});