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JavaScript Snippets from Everywhere
+1 === 1;
+0 === 0;
+undefined == NaN;
+null === 0;
+({1:2,2:3}).length == NaN
// Underscore -> https://github.com/documentcloud/underscore/blob/master/underscore.js#L80
var each = _.each = _.forEach = function(obj, iterator, context) {
if (obj == null) return;
if (nativeForEach && obj.forEach === nativeForEach) {
obj.forEach(iterator, context);
} else if (obj.length === +obj.length) {
for (var i = 0, l = obj.length; i < l; i++) {
if (iterator.call(context, obj[i], i, obj) === breaker) return;
}
} else {
for (var key in obj) {
if (_.has(obj, key)) {
if (iterator.call(context, obj[key], key, obj) === breaker) return;
}
}
}
};
// Instead of
Boolean(obj);
// Can use
!!obj;
!!~-1 === false; // only -1 will return false
/*
Explanation -> http://stackoverflow.com/a/10582345/889972
-1 = 1111 1111 1111 1111 1111 1111 1111 1111b
~-1 = 0000 0000 0000 0000 0000 0000 0000 0000b // ~ = bitwise not = invert all bits
*/
!!~2 === true;
!!~NaN === true;
!!~undefined === true;
// http://www.cnblogs.com/linjisong/archive/2012/08/25/2654852.html
// + : 除了加(+)之外,如果操作数不是Number类型,
// 会自动调用Number()转换为Number类型再进行计算。
// -: 对于加减(+-),除了作为算术运算符。还可以作为一元操作符(
// 一元减则是在一元加的基础之上再取其相反数。)。
// 当然,由于字符串操作中对加号(+)的重载,还可以用于将任意数值
// (的字符串)相连,这也是第1点中为什么要除了加(+),它在含有非
// Number类型值时,会将所有操作数转换为字符串相连接。
+1 === 1; //true
+0 === 0; //true
+undefined == NaN; //true
+null === 0; //true
+({1:2,2:3}).length === NaN; //true
+"0xff" === 255; //true
+"0x10" === 16; //true
+"010" === 10; //true
+"100" === 100; //true
// Usage in Underscore ->
// https://github.com/documentcloud/underscore/blob/master/underscore.js#L80
var each = _.each = _.forEach = function(obj, iterator, context) {
if (obj == null) return;
if (nativeForEach && obj.forEach === nativeForEach) {
obj.forEach(iterator, context);
} else if (obj.length === +obj.length) {
for (var i = 0, l = obj.length; i < l; i++) {
if (iterator.call(context, obj[i], i, obj) === breaker) return;
}
} else {
for (var key in obj) {
if (_.has(obj, key)) {
if (iterator.call(context, obj[key], key, obj) === breaker) return;
}
}
}
};
// Sugar -> https://github.com/zhuochun/Sugar/blob/master/release/1.3/sugar-1.3-full.development.js#L29
var ClassNames = 'Array,Boolean,Date,Function,Number,String,RegExp'.split(',');
var isArray = buildClassCheck(ClassNames[0]);
var isBoolean = buildClassCheck(ClassNames[1]);
var isDate = buildClassCheck(ClassNames[2]);
var isFunction = buildClassCheck(ClassNames[3]);
var isNumber = buildClassCheck(ClassNames[4]);
var isString = buildClassCheck(ClassNames[5]);
var isRegExp = buildClassCheck(ClassNames[6]);
function buildClassCheck(type) {
return function(obj) {
return isClass(obj, type);
}
}
function isClass(obj, str) {
return Object.prototype.toString.call(obj) === '[object '+str+']';
}
// Underscore
_.isNaN = function(obj) {
return _.isNumber(obj) && obj != +obj;
};
_.isBoolean = function(obj) {
return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
};
_.isUndefined = function(obj) {
return obj === void 0;
};
_.isElement = function(obj) { // DOM Element
return !!(obj && obj.nodeType === 1);
};
_.isObject = function(obj) {
return obj === Object(obj);
};
// jQuery
isEmptyObject = function( obj ) {
var name;
for ( name in obj ) {
return false;
}
return true;
}
// Instead of using
Math.floor(3.14159); // = 3
// Can also use
0 | 3.14159; // = 3
// Or
~~3.14156; // = 3
/*
Explanation: http://stackoverflow.com/questions/5533387/javascript-operator
When using the bitwise or operator in JavaScript, the runtime has to convert
the operands to 32 bit integers before it can proceed. Doing this chops away
the fractional part, leaving you with just an integer left behind. Bitwise OR
of zero is a no op (well, a no op in a language that has true integers) but
has the side effect of flooring in JavaScript.
*/
// Underscore -> https://github.com/documentcloud/underscore/blob/master/underscore.js#L1004
_.random = function(min, max) {
if (max == null) {
max = min;
min = 0;
}
return min + (0 | Math.random() * (max - min + 1));
};
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