Performance improvements and internal simplification

[james-pre]

This PR makes a number of performance improvements, including:

• Inlining function calls (time)
• Inlining single-use variables (memory)
• Inlining single-use functions (time)
• Using const instead of let (allows for better V8 optimizations)
• Using ternary expressions (more readable, less code, potential V8 optimizations)
• Eliminating duplicate function calls