Cannot read properties of undefined when chaining methods [duplicate]

Solution 1:

You are calling hasDiff without binding it to the correct this object. Since you have strict mode enabled, the this that hasDiff is referring to when invoked outside of a someObject.hasDiff(...) syntax is then undefined (without strict mode it would be the global object).

Instead of passing this.hasDiff to isListEqualToRows, you need to pass either this.hasDiff.bind(this) or (item, row) => this.hasDiff(item, row).

_{Alternatively, add a thisArg argument to isListEqualToRows where you pass this from the caller's scope and then invoke hasDiffFunction as hasDiffFunction.call(thisArg, object, row) instead of hasDiffFunction(object, row).}

See also: How does the "this" keyword work?