axios发送post请求后台接受不到问题

var params = new URLSearchParams();
params.append('param1', 'value1');
params.append('param2', 'value2');
axios.post('/foo', params);

var _this = this
_this.$ajax.post('http://localhost/mobile/index/login',{par1:_this.par1,par2:_this.par2}
,{headers: {'Content-Type':'application/x-www-form-urlencoded;charset=UTF-8'}})
.then(function (response) {
_this.$router.push({path:'/index'})
}).catch(function (error) {
console.log(error);
});