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selectWhere() : Filter Collection by Condition

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Summary

Filter a collection to return only items where a specific property matches a value.

Signature 

selectWhere(collection, propertyName, value)

Parameters

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

Returns

Type: Array

A new array containing only items where the specified property equals the given value.

Examples

Filter by Status 

<h3>Active Tasks</h3>

  <p> - Priority: </p>

Data:

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

Output:

<h3>Active Tasks</h3>
<p>Task 1 - Priority: high</p>
<p>Task 3 - Priority: low</p>

Filter and Calculate 

<h3>Category Sales</h3>
<p>Electronics: $</p>
<p>Books: $</p>
<p>Clothing: $</p>

Data:

doc.Params["model"] = new {
    products = new[] {
        new { name = "Laptop", category = "Electronics", sales = 2500.00 },
        new { name = "Phone", category = "Electronics", sales = 1800.00 },
        new { name = "Novel", category = "Books", sales = 350.00 },
        new { name = "Shirt", category = "Clothing", sales = 450.00 },
        new { name = "Tablet", category = "Electronics", sales = 1200.00 }
    }
};

Output:

<h3>Category Sales</h3>
<p>Electronics: $5500</p>
<p>Books: $350</p>
<p>Clothing: $450</p>

Filter Boolean Properties 

<h3>Verified Users ()</h3>

  <p> - </p>

Data:

doc.Params["model"] = new {
    users = new[] {
        new { name = "Alice", email = "alice@example.com", verified = true },
        new { name = "Bob", email = "bob@example.com", verified = false },
        new { name = "Charlie", email = "charlie@example.com", verified = true }
    }
};

Output:

<h3>Verified Users (2)</h3>
<p>Alice - alice@example.com</p>
<p>Charlie - charlie@example.com</p>

Multi-Step Filtering 

<h3>High Priority Active Tasks</h3>

  
    <p> - Due: </p>

Data:

doc.Params["model"] = new {
    tasks = new[] {
        new { name = "Fix Bug", status = "active", priority = "high", dueDate = new DateTime(2024, 3, 20) },
        new { name = "Write Docs", status = "active", priority = "low", dueDate = new DateTime(2024, 3, 25) },
        new { name = "Deploy", status = "active", priority = "high", dueDate = new DateTime(2024, 3, 18) },
        new { name = "Review Code", status = "completed", priority = "high", dueDate = new DateTime(2024, 3, 15) }
    }
};

Output:

<h3>High Priority Active Tasks</h3>
<p>Fix Bug - Due: Mar 20</p>
<p>Deploy - Due: Mar 18</p>

Notes

  • Returns empty array if no items match
  • Uses equality comparison (==) for matching
  • Case-sensitive for string comparisons
  • Does not modify original collection
  • Property must exist on items (null properties match null value)
  • Useful for:
    • Status-based filtering
    • Category segregation
    • Boolean flag filtering
    • Multi-step filtering pipelines
    • Conditional aggregations
  • For counting filtered items, use countOf() instead
  • For finding single item, use firstWhere()
  • Can be nested for complex filters
  • Performance: O(n) - iterates through entire collection

See Also