<script>
    console.log(1);
    setTimeout(function() {
        console.log(2);
    }, 0);
    $.ajax({
        url: "example.php",  //php文件 echo '3';
        type: 'GET',
        success: function(data) {
            console.log(data);
        },
    })
    new Promise(function(resolve, reject) {
        console.log(4);
        resolve();
    }).then(function() {
        console.log(5);
    }).then(function() {
        console.log(6);
    })
    console.log(7);
</script>