Javascript: Passing an array to a function does not work?

Question

I have a function that builds an array with push.

function one(resultsArray) {
 activity_basic_weight = 9;
 for (i in resultsArray) {
 score = 0;
 score = resultsArray[i].var_a * activity_basic_weight;
 score = Math.round(score * 100) / 100;
 if (score >= 80) 
 {
 verygoodCategories1.push({
 score: score,
 name: i,
 url: resultsArray[i].url
 });
 } 
 else if (score <= 79) 
 {
 ... 
 }
 }
 two(verygoodCategories1, ...); 
}
function two(verygoodCategories1, ...) {
 alert(verygoodCategories1.length); // = 7, correct;
 // here comes the problem:
 for (var i = 0; i < verygoodCategories1.length; i++) {
 //this throws "Error: TypeError: verygoodCategories1 is undefined"
 }
}

I am new at Javascript. Am I doing something fundamentally wrong?

This is pseudocode, but I made sure that at least the variable names are correct etc.

Any ideas?

Thanks

J

• MVCDS: Where are you initializing verygoodCategories1 as an array?
• jwatts1980: Where are you initializing verygoodCategories1 as an array? Should be at least a verygoodCategories1 = []; in there somewhere.
• Chris Tavares: Also, you should not use for-in loops on arrays. stackoverflow.com/questions/500504/…
• Bergi: Can you please give use the actual code (including the invocation of one(...)), not pseudocode? Some var statements would be nice there :-)
• Jacques: Here is a fiddle with the actual code: jsfiddle.net/zd1y6w8e

Answer 1

Declaring variables is important. Also, as mentioned in the comments, don't use for...in. Maybe someday you will want to use that but not today.

Here is your pseudo code written so that it could actually work.

var a = [{var_a:100},{var_a:90},{var_a:81},{var_a:81},{var_a:91},{var_a:101}];
function one(resultsArray) {
 //This is critical to later using it as an array.
 var verygoodCategories1 = [];
 // you should always initialize a variable with var. 
 // You can not do it but thats bad form. You will
 // pollute the global space and people will dislike you.
 var activity_basic_weight = 9;
 for (var i = 0; i < resultsArray.length; i++) {
 var score = resultsArray[i].var_a * activity_basic_weight;
 score = Math.round(score * 100) / 100;
 if (score >= 80) 
 {
 verygoodCategories1.push({
 score: score,
 name: i,
 url: resultsArray[i].url
 });
 } 
 else if (score <= 79) 
 {
 //...
 }
 }
 two(verygoodCategories1); 
}
function two(verygoodCategories1) {
 alert(verygoodCategories1.length); // = 7, correct;
 for (var i = 0; i < verygoodCategories1.length; i++) {
 //no more errors!
 }
}
one(a);

Answer 2

Assign the array parameter to a variable:

function two(verygoodCategories1, ...) {
 alert(verygoodCategories1.length); // = 7, correct;
 var goodCategories=verygoodCategories1;
 var goodCategoriesLength=goodCategories.length;
 for (var i = 0; i < goodCategoriesLength; i++) {
 console.log(goodCategories[i]);
 }
}

• Gangadhar Jannu: @Jacques Would you comment your code in the jsfiddle, where the problem is like what is the array, when it is being "undefined"

Answer 3

Go to your function one(resultArray). just before the for, you might want to declare the array there like:

verygoodCategories1 = new Array();

• Matt Rabe: This looks like bad advice. If you define verygoodCategories1 as a new array in the location you suggest, it will wipe out the contents each time it loops...
• Akah: Ah yeah, i missed seeing the for loop above. The array should be created as the first statement in the function.