Question

import tensorflow as tf
import numpy as np

def entry_stop_gradients(target, mask):
    mask_h = tf.abs(mask-1)
    return tf.stop_gradient(mask_h * target) + mask * target

mask = np.array([1., 0, 1, 1, 0, 0, 1, 1, 0, 1])
mask_h = np.abs(mask-1)

emb = tf.constant(np.ones([10, 5]))

matrix = entry_stop_gradients(emb, tf.expand_dims(mask,1))

parm = np.random.randn(5, 1)
t_parm = tf.constant(parm)

loss = tf.reduce_sum(tf.matmul(matrix, t_parm))
grad1 = tf.gradients(loss, emb)
grad2 = tf.gradients(loss, matrix)
print matrix
with tf.Session() as sess:
    print sess.run(loss)
    print sess.run([grad1, grad2])

上面的代码出了什么问题？如果function formatToStandardizedDate(from, to){ const from_date = moment(from); if(to){ let to_date = moment(to); }else{ let to_date = null; } } console.log(formatToStandardizedDate("2017-04-19 00:00:00",null))为空，则至少为to分配一个空值，但我得到了to_date未定义错误的错误。为什么呢？

Answer 1

您不能对let关键字使用相同的变量名称。如果你试图这样做会抛出错误。

相反，你必须使用三元运算符：

let to_date = to ? moment(to) : null;

或在函数上面声明一次并更新变量

function formatToStandardizedDate(from, to){
    const from_date = moment(from);
    let to_date = null; // initialize the variable with null
    if(to)
      to_date = moment(to); // <---here update the variable with new value.
}

_{根据JaredSmith的评论进行了更新，这似乎很好。}

let变量未定义

1 个答案: