Hi,
If you want to access attributes in a datasource, you need to specify attribute properties in your widget XML and reference them to the datasource
https://docs.mendix.com/apidocs-mxsdk/apidocs/pluggable-widgets-property-types/#attribute
An example:
<property key="myStringProp" type="attribute" dataSource="EntityList" required="false">
<caption>My property</caption>
<description>My property description</description>
<attributeTypes>
<attributeType name="String"/>
</attributeTypes>
</property>
To get the value in your widget code:
props.myStringProp.get(item).value
For decimal or date, use displayValue to get formatted value
The item is one item in your datasource items array so you need to loop over the array in your widget code using standard JavaScript for loop