JavaScript efficiency tuning experience _ javascript skills

Sometimes you need to use the following knowledge when using multiple characters. 1. Put the definition of the number of cycles in the external body of the Loop: It seems that all languages are the same, and the effect on more than 100 elements is becoming more and more obvious. That is to say, for (var I = 0; I = 0; I --). After testing, I found that the efficiency is not much different from that of the ascending cycle.
2. Change the multi-layer object reference to a shorter path reference: In JavaScript, this problem is very obvious, such as the proposalNo domain var proposalNoField = fm. proposalNo. There is a huge difference between proposalNoField. value and fm. proposalNo. value in a loop (more than 100 times. Therefore, try to shorten the access path by using intermediate variables.
3. impact of third-party JavaScript packages: JavaScript supports prototypes, such as prototype. js modifies some of the behavior of the Array. Sometimes the code you write is okay, but if the prototype is modified, the problem also occurs, such as prototype. in js 1.4, there is a Bug. In some cases, array sorting will lead to an endless loop.