JavaScript, like any language, requires us to be judicious in the use of certain language features. Overuse of some features can decrease performance, while some techniques can be used to increase performance.
Remember that premature optimization is the root of all evil. Write clear, correct code first, then if you have performance problems, use a profiler to look for specific areas to improve. Don’t waste time optimizing code that’s not affecting the overall performance in a meaningful way.
Measure, measure, measure. Performance can often be counter intuitive, and changes over time. What’s faster now might not be in the future, and can depend on your use case. Make sure any optimizations you make are actually improving, not hurting performance, and that the change is worthwhile.
Avoid try/catch in performance-critical functions
Benchmarking your code - measuring execution time
Cache (memoize) heavy-computing functions
Initializing object properties with null
Reuse objects rather than recreate
Prefer local variables to globals attributes and indexed values