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countOf() : Count Items Matching Condition

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Summary

Count the number of items in a collection where a specific property matches a value.

Signature 

countOf(collection, propertyName, value)

Parameters

Parameter Type Required Description
collection Array/Collection Yes The collection to search
propertyName String Yes Name of the property to check
value Any Yes Value to match against

Returns

Type: Number (Integer)

The number of items where the specified property equals the given value.

Examples

Count by Status 

<h3>Task Status</h3>
<p>Active: </p>
<p>Completed: </p>
<p>Pending: </p>

Data:

doc.Params["model"] = new {
    tasks = new[] {
        new { name = "Task 1", status = "active" },
        new { name = "Task 2", status = "completed" },
        new { name = "Task 3", status = "active" },
        new { name = "Task 4", status = "pending" },
        new { name = "Task 5", status = "completed" }
    }
};

Output:

<h3>Task Status</h3>
<p>Active: 2</p>
<p>Completed: 2</p>
<p>Pending: 1</p>

Boolean Property Count 

<p>Verified users: </p>
<p>Unverified users: </p>

Data:

doc.Params["model"] = new {
    users = new[] {
        new { name = "Alice", verified = true },
        new { name = "Bob", verified = false },
        new { name = "Charlie", verified = true },
        new { name = "Diana", verified = true }
    }
};

Output:

<p>Verified users: 3</p>
<p>Unverified users: 1</p>

Inventory by Category 

<h3>Inventory Summary</h3>

  <p>:  items</p>

Data:

doc.Params["model"] = new {
    categories = new[] { "Electronics", "Books", "Clothing" },
    products = new[] {
        new { name = "Laptop", category = "Electronics" },
        new { name = "Phone", category = "Electronics" },
        new { name = "Novel", category = "Books" },
        new { name = "Shirt", category = "Clothing" },
        new { name = "Tablet", category = "Electronics" }
    }
};

Output:

<h3>Inventory Summary</h3>
<p>Electronics: 3 items</p>
<p>Books: 1 items</p>
<p>Clothing: 1 items</p>

Priority Distribution 

<h3>Priority Distribution</h3>
<p>High:  (%)</p>
<p>Medium:  (%)</p>
<p>Low:  (%)</p>

Data:

doc.Params["model"] = new {
    issues = new[] {
        new { id = 1, priority = "high" },
        new { id = 2, priority = "medium" },
        new { id = 3, priority = "high" },
        new { id = 4, priority = "low" },
        new { id = 5, priority = "high" }
    }
};

Output:

<h3>Priority Distribution</h3>
<p>High: 3 (60%)</p>
<p>Medium: 1 (20%)</p>
<p>Low: 1 (20%)</p>

Notes

  • Uses equality comparison (==) to match values
  • Case-sensitive for string comparisons
  • Returns 0 if no items match
  • Property must exist on all items (or be null)
  • Useful for:
    • Grouping statistics
    • Category counting
    • Boolean flag tallies
    • Distribution analysis
    • Filtering summaries
  • For simple collection size, use count() instead
  • For more complex conditions, combine with selectWhere() and count()

See Also