ajax

XMLHttpRequest 对象

function ajax(url) {
    const p = new Promise((resolve, reject) => {
        const xhr = new XMLHttpRequest()
        xhr.open('GET', url, true)
        xhr.onreadystatechange = function() {
            if (xhr.readyState === 4) {
                if (xhr.status === 200) {
                    resolve(
                        JSON.parse(xhr.responseText)
                    )
                } else if (xhr.status === 404 || xhr.status === 500) {
                    reject(new Error('404 not found'))
                }
            }
        }
        xhr.send(null)
    })
    return p
}

const url = '/data/test.json'
ajax(url)
    .then(res => console.log(res))
    .catch(err => console.error(err))

jquery ajax使用

$.ajax({
    url: '/api/user',
    type: 'post',
    data: {
        id: 1,
        name:'张三'
    },
    dataType: 'json',
    async: false,
    contentType: 'application/json; charset=UTF-8',
    success: function(data) {

    }
})