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JavaScript JavaScript Loops, Arrays and Objects Tracking Data Using Objects Accessing All of the Properties in an Object

Posted by ammarkhan
.a{fill-rule:evenodd;}techdegree
ammarkhan
Front End Web Development Techdegree Student 21,661 Points

getting value for the key:value pair.

I am unable to understand and hence pass how to pass value into the loop, from my understand 

for(key in value){
    console.log(key,':', person[value]);
}

i might be wrong as it is confusing and i cannot understand on how to access key value pair.

script.js 
var shanghai = {
  population: 14.35e6,
  longitude: '31.2000 N',
  latitude: '121.5000 E',
  country: 'CHN'
};
for(var key in shanghai){
    console.log(key[shanghai], ':' ,shanghai['key'])
 }
index.html 
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript Objects</title>
</head>
<body>
<script src="script.js"></script>
</body>
</html>

2 Answers

Eduardo Parra San Jose
Eduardo Parra San Jose
12,579 Points
Eduardo Parra San Jose
Eduardo Parra San Jose
12,579 Points

Hi,

I'll try to help. When you use for in to loop through an object, the variable holds the value of the property. So when you do:

var shanghai = {
  population: 14.35e6,
  longitude: '31.2000 N',
  latitude: '121.5000 E',
  country: 'CHN'
};

for(var key in shanghai){

 }

In the first iteration key will be "population", in the next iteration key will be "longitude" and so on. In order to log the property and value to the console:

  // as key hold the value of the property
  // shangai[key] will give you the value for that property
for(var key in shanghai){
  console.log(key, ":", shanghai[key]);
}

The final code will look like:

var shanghai = {
  population: 14.35e6,
  longitude: '31.2000 N',
  latitude: '121.5000 E',
  country: 'CHN'
};

for(var property in shanghai) {
  console.log(property, ":", shanghai[property]);
}

I hope it helps. Have a nice day :)

ammarkhan
.a{fill-rule:evenodd;}techdegree
ammarkhan
Front End Web Development Techdegree Student 21,661 Points

Why can't we use + to concat javascript variable, why use , ":",?

Nicholas Vogel
Nicholas Vogel
12,318 Points
Nicholas Vogel
Nicholas Vogel
12,318 Points

The solution is pretty simple, and it follows the formula you provided in your first code block. Instead of putting 

console.log(key[shanghai]))

it should just be 

console.log(key, ':', shanghai[key]);

Note: you also forgot a ; at the end of your console.log and the key in the square bracket shouldn't have quotes. It looks like you understand this from your first code block, but feel free to ask more questions!