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Need to start a Nintex workflow from within your TypeScript application? Here is a service class which wraps all the gubbins of the asmx service and can be called via a single function that returns a promise.

Parameters:

Workflow Name
List Name
Item ID
Workflow Parameters (as an object {parameter:value,...} ).

import { Web } from '@pnp/sp';
import { xml2json } from 'xml-js';

export class NintexWfService {

    private envStartNintexWorkflow: string;
    private web: Web;
    private digest: string;

    constructor() {
        this.web = new Web(_spPageContextInfo.webAbsoluteUrl);

        this.envStartNintexWorkflow = 
            "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
            "<soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\">" +
            "<soap:Body>" +
            "<StartWorkflowOnListItem xmlns=\"http://nintex.com\">" +
            "<itemId>ITEM_ID</itemId>" +
            "<listName>LIST_NAME</listName>" +
            "<workflowName>WORKFLOW_NAME</workflowName>" +
            "<associationData>WORKFLOW_DATA</associationData>" +
            "</StartWorkflowOnListItem>" +
            "</soap:Body>" +
            "</soap:Envelope>";

        this.digest = '';
    }

    public startNintexWorkflow(wfName: string, listName: string, itemId: number, wfParameters?: {}): Promise<any> {

        return new Promise((resolve, reject) => {
            this.getDigest()
                .then(digest => {
                    let xmlParameters: string = '';
                    if (wfParameters) {
                        let totalParams: number = 0;
                        xmlParameters = '<Data>';
                        Object.keys(wfParameters).map((k, i) => {
                            if (wfParameters[k]) {
                                xmlParameters += '<' + k + '>' + wfParameters[k] + '</' + k + '>';
                                totalParams++;
                            }
                        });
                        xmlParameters += '</Data>';
                        if (totalParams > 0) {
                            xmlParameters = this.xmlEscape(xmlParameters);
                        }
                        else {
                            xmlParameters = '';
                        }
                    }
                    const url = _spPageContextInfo.webAbsoluteUrl + '/_vti_bin/NintexWorkflow/Workflow.asmx';
                    const headerData = {
                        'Accept': 'text/xml',
                        'Content-Type': 'text/xml; charset=utf-8',
                        'SOAPAction': 'http://nintex.com/StartWorkflowOnListItem',
                        'X-RequestDigest': digest
                    };

                    let soap = this.envStartNintexWorkflow;
                    soap = soap.replace('ITEM_ID', <string>itemId.toString());
                    soap = soap.replace('LIST_NAME', <string>listName);
                    soap = soap.replace('WORKFLOW_NAME', <string>wfName);
                    soap = soap.replace('WORKFLOW_DATA', xmlParameters);

                    return fetch(
                        url,
                        {
                            method: 'POST',
                            headers: headerData,
                            body: soap,
                            credentials: 'same-origin'
                        }
                    );
                })
                .then((data) => {
                    if (!data.ok) {
                        reject(data.statusText)
                    }
                    else {
                        data.clone().text().then(xml => {
                            let wfGuid = '';
                            try {
                                var jsonRes: any = JSON.parse(xml2json(xml));
                                wfGuid = jsonRes.elements[0].elements[0].elements[0].elements[0].elements[0].text;
                            }
                            catch (err) {
                                wfGuid = '';
                            }
                            resolve(wfGuid);
                        });
                    }
                })
                .catch(err => {
                    reject(err);
                });
        });
    }

    private xmlEscape(str: string): string {
        return String(str).replace(/&amp;/g, '&amp;').replace(/"/g, '"').replace(/'/g, ''').replace(/</g, '<').replace(/>/g, '>');
    }

    private getDigest(): Promise<any> {

        return new Promise((resolve, reject) => {
            if (this.digest !== '') {
                resolve(this.digest);
            }
            else {
                fetch(
                    _spPageContextInfo.webAbsoluteUrl + '/_api/contextinfo',
                    {
                        method: 'POST',
                        headers: { 'Accept': 'application/json; odata=verbose', 'content-type': 'application/json; odata=verbose' },
                        credentials: 'same-origin'
                    })
                    .then((response) => {
                        return response.text();
                    })
                    .then((data) => {
                        const jsonVal = JSON.parse(data);
                        if (jsonVal.d &amp;&amp; jsonVal.d.GetContextWebInformation &amp;&amp; jsonVal.d.GetContextWebInformation.FormDigestValue) {
                            this.digest = jsonVal.d.GetContextWebInformation.FormDigestValue;
                            resolve(this.digest);
                        }
                        else {
                            reject(jsonVal);
                        }
                    })
                    .catch((response) => {
                        reject(response);
                    });
            }
        });
    }
}

Notice we’re using fetch() to make the calls.

To call it:

const nwfs = new NintexWfService();
nwfs.startNintexWorkflow(
          'Industrious Workflow',
          'Documents',
          321,
          { MyParameter: 'MyP@r@m3t3r' })
     .then((wfId) => {
          console.log('Workflow GUID: ' + wfId + ' started!');
     });