Javascript函数返回undefined而不是int

Question

My js/jquery function does not work properly and instead of INT returns undefined.

function __getLastSelectedCategory(table_id) {
    if ( jQuery('.categories_table[data-table-id="1"]').find('td.active').length > 0 ){
        console.log('check1');
        if (table_id != '0') {
            console.log('check2');
            var checkTableId = parseInt(table_id) - 1;
            var table = jQuery('.cl_categories_display ').find('table[data-table-id="' + checkTableId + '"]');

            if (table.find('td.active').length > 0) {
                console.log('check3');
                console.log('table id: ' + table.find('td.active').data('category-id'));
                return table.find('td.active').data('category-id');
            } else {
                console.log('check4');
                __getLastSelectedCategory(checkTableId);
            }
        } else {
            console.log('check5');
            var lastTable = jQuery('.cl_categories_display ').find('table:last');
            var lastTableId = lastTable.data('table-id');

            if (lastTable.find('td.active').length > 0) {
                console.log('check6');
                return lastTable.find('td.active').data('category-id');
            } else {
                console.log('check7');
                __getLastSelectedCategory(lastTableId);
            }
        }
    } else {
        console.log('check8');
        return null;
    }
}

when I run this function I see in console:

• check 1
• check 5
• check 7
• check 1
• check 2
• check 3
• table id: 1
• last cat: undefined

so the recursion works fine, but instead of integer (console printed "table id: 1") ir returns undefined. What could be wrong?

Answer 1

You forgot return from recurse call: It returned value from the inner function to the outer, but did not return it from outer function to the caller. Try this:

    function __getLastSelectedCategory(table_id) {
        if ( jQuery('.categories_table[data-table-id="1"]').find('td.active').length > 0 ){
        console.log('check1');
        if (table_id != '0') {
            console.log('check2');
            var checkTableId = parseInt(table_id) - 1;
            var table = jQuery('.cl_categories_display ').find('table[data-table-id="' + checkTableId + '"]');

            if (table.find('td.active').length > 0) {
            console.log('check3');
            console.log('table id: ' + table.find('td.active').data('category-id'));
            return table.find('td.active').data('category-id');
            } else {
            console.log('check4');
            return __getLastSelectedCategory(checkTableId);
            }
        } else {
            console.log('check5');
            var lastTable = jQuery('.cl_categories_display ').find('table:last');
            var lastTableId = lastTable.data('table-id');

            if (lastTable.find('td.active').length > 0) {
            console.log('check6');
            return lastTable.find('td.active').data('category-id');
            } else {
            console.log('check7');
            return __getLastSelectedCategory(lastTableId);
            }
        }
        } else {
        console.log('check8');
        return null;
        }
    }