How to prevent sending repeated ajax requests

Question

if the ajax request has not been returned successfully in the first time,i want to ignore the second request until the first request returns successful response.

public static POST<T>(url: string, data): Promise<T> {
    var p = new Promise((resolve, reject) => {
        $.ajax({
            url: url,
            data: data,
            type: "POST",
            cache: false,
            success: function (response: HttpResponse) {
                   //success
            },
            error: function (response) {
                reject("error");
            }
        });
    });

    p.catch((err) => {
        //error
    });

    return p;
}

I solved this problem already.The code as follows:

var flag: { Url: string, Data: any }[];
flag = [];
public static POST<T>(url: string, data): Promise<T> {
  for (var i = 0; i < flag.length; i++) {
        if (flag[i].Url == url && CompareObjectEqual(flag[i].Data, data)) {
            return;
        }
    }
    var postInfo = {
        Url: url,
        Data: data
    };
    flag.push(postInfo);
  var p = new Promise((resolve, reject) => {
    $.ajax({
        url: url,
        data: data,
        type: "POST",
        cache: false,
        success: function (response: HttpResponse) {
               flag = [];
               //success
        },
        error: function (response) {
            reject("error");
        }
    });
  });

  p.catch((err) => {
    flag = [];
    //error
  });

  return p;
}

The function of CompareObjectEqual:

function CompareObjectEqual(a, b) {
  if (!(a instanceof Object && b instanceof Object)) {
    return a === b;
  }

  var aProps = Object.getOwnPropertyNames(a);
  var bProps = Object.getOwnPropertyNames(b);

  if (aProps.length != bProps.length) {
    return false;
  }

  for (var i = 0; i < aProps.length; i++) {
    var propName = aProps[i];
    if ((a[propName] instanceof Object) && (b[propName] instanceof Object)){
        CompareObjectEqual(a[propName], b[propName]);
    } else {
        if (a[propName] !== b[propName]) {
            return false;
        }
    }
  }

  return true;
}

and how to judge if the two requests are the same.if same,to prevent — foxery, Jun 27 '17 at 03:05
It seems like you want the second method to be fired after the first. In that case, why not use the `done()` or then `methods()` [More details](https://stackoverflow.com/questions/5436327/jquery-deferreds-and-promises-then-vs-done). You can even call Post from the success method as well. — Nikhil Mathew, Jun 27 '17 at 04:12

score 0 · Answer 1 · answered Jun 27 '17 at 02:22

I'm not certain how your are calling the promise, but you can always use a flag or variable to signal that a request has been sent and then toggle that flag / variable when the response is returned. Also, I assume you are using Typescript with this so I wrote my response using that syntax.

postSubmitted = false;

public static POST<T>(url: string, data): Promise<T> {

    if (postSubmitted) { return };
    postSubmitted = true;

    var p = new Promise((resolve, reject) => {
        $.ajax({
            url: url,
            data: data,
            type: "POST",
            cache: false,
            success: function (response: HttpResponse) {
                postSubmitted = false;
                   //success
            },
            error: function (response) {
                postSubmitted = false;
                reject("error");
            }
        });
    });

    p.catch((err) => {
        //error
    });

    return p;
}

How to prevent sending repeated ajax requests

1 Answers1