javascript - Coffeescript 按索引删除数组值

Question

我有一个对象数组，我想通过索引删除一个值。我有一个方法，将要删除的值传递给该方法，找到传递的参数值:

remove: (val) ->
  for el, index in @arr
    if el is val
      # remove el from @arr...

CoffeeScript website说得很清楚，为了替换我想要的元素，我必须做 @arr[index] = 'something'，但没有说要完全删除它。

Answer 1

只需使用.splice():

for index, elem in @arr
    @arr.splice index, 1 if elem is val

如果您不关心 Internet Explorer 7 或 8，您可以进一步简化它:

@arr.splice @arr.indexOf(val), 1

这假定该元素存在于数组中，否则它会删除最后一个元素。如果您需要检查它是否存在，您可以使用一个小技巧:

@arr.splice (@arr.indexOf(val)+1 or @arr.length+1)-1, 1

与“仅咖啡”过滤器解决方案相比，您获得 4-8 倍的性能(在 Chrome 中):

Removing 5 random elements from an array with 10.000.000 integers

cumulative execution time after each removed element

filter method

• 197ms
• 422ms
• 626ms
• 847ms
• 1087ms

splice method

• 33ms
• 83ms
• 142ms
• 198ms
• 255ms

splice and indexOf method

• 27ms
• 70ms
• 88ms
• 116ms
• 134ms

测试代码 - 快速而肮脏(不考虑两次随机选择相同的值):

log "coffee method"
arr = [0..9999999]
length = arr.length
start = new Date().getTime()
for num in [1..5]
    val = Math.round(Math.random() * length)
    do (val) -> arr = (x for x in arr when x isnt val)
    log new Date().getTime()-start+"ms"

log "splice method"
arr = [0..9999999]
length = arr.length
start = new Date().getTime()
for num in [1..5]
    val = Math.round(Math.random() * length)
    for index, elem in arr
        arr.splice index, 1 if elem is val
    log new Date().getTime()-start+"ms"

log "splice method with indexOf()"
arr = [0..9999999]
length = arr.length
start = new Date().getTime()
for num in [1..5]
    val = Math.round(Math.random() * length)
    arr.splice arr.indexOf(val), 1
    log new Date().getTime()-start+"ms"

演示:http://jsfiddle.net/j9CZz/1/