Promise.all解决多层嵌套

修改前
this.getBase64(headImg).then(base64=>{
this.base64.headImg = base64;
//封面转base64
this.getBase64(codeImg).then(base64=>{
this.base64.codeImg = base64;
//二维码转base64
this.getBase64(coverImg).then(base64=>{
this.base64.coverImg = base64;
this.selInviteFun(0);
});
});
});

修改后（推荐写法）
let p1 = this.util.imageUrl2Base64(headImg).then((base64) => {
this.base64.headImg = base64;
});
let p2 = this.util.imageUrl2Base64(codeImg).then((base64) => {
this.base64.codeImg = base64;
});
let p3 = this.util.imageUrl2Base64(coverImg).then((base64) => {
this.base64.coverImg = base64;
});
Promise.all([p1, p2, p3]).then((data) => {
this.selInviteFun(0);
});