How to update Signature for a user using Script API

The settings widget is using this jQuery code to update signature , if you need a script api you can setup an automation with jQuery by setting up the manual execution

 _saveUser = function(context) {
        var data = {
            Language: $(context.languageSelector).val(),
            PrivateEmail: $(context.privateEmailSelector).val(),
            EnableFavoriteSharing: $(context.sharedFavoritesSelector).is(':checked'),
            AllowSiteToContact: $(context.allowSiteContactSelector).is(':checked'),
            AllowSitePartnersToContact: $(context.allowSitePartnersContactSelector).is(':checked'),
            EnableDisplayInMemberList: $(context.enableDisplayInMembersSelector).is(':checked'),
            TimeZoneId: $(context.timezoneSelector).val(),
            DateFormat: $(context.dateFormatSelector).val(),
            UserId : context.userId
        };

        if ($(context.editorListSelector).length > 0)
            data.EditorType = $(context.editorListSelector).val();

        if ($(context.receiveEmailsSelector).length > 0)
            data.ReceiveEmails = $(context.receiveEmailsSelector).is(':checked');
        if ($(context.enableHtmlEmailSelector).length > 0)
            data.EnableHtmlEmail = $(context.enableHtmlEmailSelector).is(':checked');

        if (context.getSignature)
        {
            data.Signature = context.getSignature();
        }

        if ($(context.enableUserSignaturesSelector).length > 0)
        {
            data.EnableUserSignatures = $(context.enableUserSignaturesSelector).is(':checked');
        }

        if ($(context.conversationContactType).length > 0)
        {
            data.ConversationContactType = $('input:checked', $(context.conversationContactType)).val();
        }

        if ($(context.enablePresenceTracking).length > 0) {
            data.EnablePresenceTracking = $(context.enablePresenceTracking).is(':checked');
        }

        return $.telligent.evolution.put({
            url: $.telligent.evolution.site.getBaseUrl() + 'api.ashx/v2/users/{UserId}.json?IncludeFields=User.Id',
            data: data,
            dataType: 'json',
            defaultErrorMessage: context.saveErrorText
        });

The settings widget is using this jQuery code to update signature , if you need a script api you can setup an automation with jQuery by setting up the manual execution

 _saveUser = function(context) {
        var data = {
            Language: $(context.languageSelector).val(),
            PrivateEmail: $(context.privateEmailSelector).val(),
            EnableFavoriteSharing: $(context.sharedFavoritesSelector).is(':checked'),
            AllowSiteToContact: $(context.allowSiteContactSelector).is(':checked'),
            AllowSitePartnersToContact: $(context.allowSitePartnersContactSelector).is(':checked'),
            EnableDisplayInMemberList: $(context.enableDisplayInMembersSelector).is(':checked'),
            TimeZoneId: $(context.timezoneSelector).val(),
            DateFormat: $(context.dateFormatSelector).val(),
            UserId : context.userId
        };

        if ($(context.editorListSelector).length > 0)
            data.EditorType = $(context.editorListSelector).val();

        if ($(context.receiveEmailsSelector).length > 0)
            data.ReceiveEmails = $(context.receiveEmailsSelector).is(':checked');
        if ($(context.enableHtmlEmailSelector).length > 0)
            data.EnableHtmlEmail = $(context.enableHtmlEmailSelector).is(':checked');

        if (context.getSignature)
        {
            data.Signature = context.getSignature();
        }

        if ($(context.enableUserSignaturesSelector).length > 0)
        {
            data.EnableUserSignatures = $(context.enableUserSignaturesSelector).is(':checked');
        }

        if ($(context.conversationContactType).length > 0)
        {
            data.ConversationContactType = $('input:checked', $(context.conversationContactType)).val();
        }

        if ($(context.enablePresenceTracking).length > 0) {
            data.EnablePresenceTracking = $(context.enablePresenceTracking).is(':checked');
        }

        return $.telligent.evolution.put({
            url: $.telligent.evolution.site.getBaseUrl() + 'api.ashx/v2/users/{UserId}.json?IncludeFields=User.Id',
            data: data,
            dataType: 'json',
            defaultErrorMessage: context.saveErrorText
        });