Javascript OOP can't get property -

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i'm trying rewrite code oop approach, stuck in something. there example :

   var counter = {     column: {     estimation: "tr td:nth-child(3)",     worked:     "tr td:nth-child(4)",     ratio:      "tr td:nth-child(5)",     difference: "tr td:nth-child(6)"     },      columnlength : function display(){         return $(this.column.estimation).length;     },

ok, works! if write same, not in function though:

    var counter = {      column: {     estimation: "tr td:nth-child(3)",     worked:     "tr td:nth-child(4)",     ratio:      "tr td:nth-child(5)",     difference: "tr td:nth-child(6)"     },      columnlength : $(this.column.estimation).length     },

it doesn't, there error : column isn't declared.

why must in function? thx in advance.

the problem when you're using this inside jquery selector $(...) value of global object window instead of object counter. so, basically, you're trying call property column of object window window.column, doesn't exist.

if run following code, you'll see what's value of this:

var counter = {   column: {   estimation: "tr td:nth-child(3)",   worked: "tr td:nth-child(4)",   ratio: "tr td:nth-child(5)",   difference: "tr td:nth-child(6)"  },   columnlength: console.log(this) }

so, why happening?

because when you're assigning executed function parameter of literal object, function executed in global context.

more info use of this: http://blog.kevinchisholm.com/javascript/context-object-literals/


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