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This article mainly introduces "what problems to pay attention to in the use of for in cycle in js". In daily operation, I believe that many people have doubts about which problems to pay attention to in the use of for in cycle in js. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts about "what problems to pay attention to in the use of for in cycle in js". Next, please follow the editor to study!

1. The for in loop does not traverse the property where enumerable is set to false; for example, the length property of the array.

2. Because for in always traverses the entire prototype chain, if the inheritance level of an object is too deep, it will affect performance.

Example

/ / modify Object.prototypeObject.prototype.bar = 1 for in foo = {moo: 2}; for (var i in foo) {console.log (I); / / output two attributes: bar and moo} at this point, the study on "what problems to pay attention to in the use of the for in loop in js" is over, hoping to solve everyone's doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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