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July 24, 2017 13:19
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Where "this" gets weird in JS
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| function test() { | |
| this.arr = [1,2,4]; | |
| this.message = "I am here"; | |
| this.fun = function() { | |
| this.arr.forEach(function(item) { | |
| console.log(this.message); // will print undefined 3 times since this refers to the global object | |
| }); | |
| } | |
| } | |
| var t = new test(); | |
| t.fun(); | |
| // In the above code, "this" WILL NOT refer to the test object but instead the global object | |
| //to get around this, you can use a variable to store "this" when it does refer to test | |
| // Since "this" still refers to the object, it will also get updated when using the substitute variable. | |
| function test2() { | |
| var self = this; | |
| self.arr = [1,2,4]; | |
| self.message = "I am here"; | |
| self.fun = function() { | |
| this.arr.forEach(function(item) { | |
| console.log(self.message); // prints "I am Here" 3 times | |
| }); | |
| } | |
| } | |
| var t2 = new test2(); | |
| t2.fun(); |
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