Add script editor to page JS

var siteUrl = '/sites/MySiteCollection';
var serverRelativeUrl = '/sites/MySiteCollection/Default.aspx';

function addWebPart() {

    var clientContext = new SP.ClientContext(siteUrl);
    var oFile = clientContext.get_web().getFileByServerRelativeUrl(serverRelativeUrl);

    var limitedWebPartManager = oFile.getLimitedWebPartManager(SP.WebParts.PersonalizationScope.shared);

    var webPartXml = '<?xml version=\"1.0\" encoding=\"utf-8\"?>' + 
        '<WebPart xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"' + 
        ' xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"' + 
        ' xmlns=\"http://schemas.microsoft.com/WebPart/v2\">' + 
        '<Title>My Web Part</Title><FrameType>Default</FrameType>' + 
        '<Description>Use for formatted text, tables, and images.</Description>' + 
        '<IsIncluded>true</IsIncluded><ZoneID></ZoneID><PartOrder>0</PartOrder>' + 
        '<FrameState>Normal</FrameState><Height /><Width /><AllowRemove>true</AllowRemove>' + 
        '<AllowZoneChange>true</AllowZoneChange><AllowMinimize>true</AllowMinimize>' + 
        '<AllowConnect>true</AllowConnect><AllowEdit>true</AllowEdit>' + 
        '<AllowHide>true</AllowHide><IsVisible>true</IsVisible><DetailLink /><HelpLink />' + 
        '<HelpMode>Modeless</HelpMode><Dir>Default</Dir><PartImageSmall />' + 
        '<MissingAssembly>Cannot import this Web Part.</MissingAssembly>' + 
        '<PartImageLarge>/_layouts/images/mscontl.gif</PartImageLarge><IsIncludedFilter />' + 
        '<Assembly>Microsoft.SharePoint, Version=13.0.0.0, Culture=neutral, ' + 
        'PublicKeyToken=94de0004b6e3fcc5</Assembly>' + 
        '<TypeName>Microsoft.SharePoint.WebPartPages.ContentEditorWebPart</TypeName>' + 
        '<ContentLink xmlns=\"http://schemas.microsoft.com/WebPart/v2/ContentEditor\" />' + 
        '<Content xmlns=\"http://schemas.microsoft.com/WebPart/v2/ContentEditor\">' + 
        '<![CDATA[This is a first paragraph!<DIV>&nbsp;</DIV>And this is a second paragraph.]]></Content>' + 
        '<PartStorage xmlns=\"http://schemas.microsoft.com/WebPart/v2/ContentEditor\" /></WebPart>';

    var oWebPartDefinition = limitedWebPartManager.importWebPart(webPartXml);
    this.oWebPart = oWebPartDefinition.get_webPart();

    limitedWebPartManager.addWebPart(oWebPart, 'Left', 1);

    clientContext.load(oWebPart);

    clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceeded), Function.createDelegate(this, this.onQueryFailed));
}

function onQuerySucceeded() {

    alert('Web Part added: ' + oWebPart.get_title());
}

function onQueryFailed(sender, args) {

    alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
}

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