var field1 = component.find("field1input");

    if(field1.get("v.validity").valid) {

        // continue processing

    } else {

        field1.showHelpMessageIfInvalid();

    }

var field1 = component.find("field1input");

    if(field1.get("v.validity").valid) {

        // continue processing

    } else {

        field1.showHelpMessageIfInvalid();

    }

var field1 = component.get("field1");

var field2 = component.get("field2");

// ...

field1.showHelpMessageIfInvalid();

field2.showHelpMessageIfInvalid();

// ...

if(field1.get("v.validity").valid &&

   field2.get("v.validity").valid // && ...

) {

    // continue processing

}