我這裡選取了三條對於提升使用者體驗非常有幫助的指令，並且我很早就將其應用在產品中。
1.頭像圖片
為了在你的應用中展示頭像圖片，你需要使用使用者的電子郵件地址，將地址轉換為小寫並使用md5加密該字串。所以聰明的做法是使用指令來做到這些，並且可以複用。
/*
* A simple Gravatar Directive
* @example
* <gravatar-image email="test@email.com" size="50"></gravatar-image>
*/
app.directive('gravatarImage',function() {
return{
restrict:'AE',
replace:true,
required:'email',
template:'<img ng-src="https://www.gravatar.com/avatar/{{hash}}?s={{size}}&d=identicon" />',
link:function(scope, element, attrs) {
attrs.$observe('email',function(value) {
if(!value) {return; }
// MD5 (Message-Digest Algorithm) by WebToolkit
varmd5=function(s){functionL(k,d){return(k<<d)|(k>>>(32-d));}functionK(G,k){varI,d,F,H,x;F=(G&2147483648);H=(k&2147483648);I=(G&1073741824);d=(k&1073741824);x=(G&1073741823)+(k&1073741823);if(I&d){return(x^2147483648^F^H);}if(I|d){if(x&1073741824){return(x^3221225472^F^H);}else{return(x^1073741824^F^H);}}else{return(x^F^H);}}functionr(d,F,k){return(d&F)|((~d)&k);}functionq(d,F,k){return(d&k)|(F&(~k));}functionp(d,F,k){return(d^F^k);}functionn(d,F,k){return(F^(d|(~k)));}functionu(G,F,aa,Z,k,H,I){G=K(G,K(K(r(F,aa,Z),k),I));returnK(L(G,H),F);}functionf(G,F,aa,Z,k,H,I){G=K(G,K(K(q(F,aa,Z),k),I));returnK(L(G,H),F);}functionD(G,F,aa,Z,k,H,I){G=K(G,K(K(p(F,aa,Z),k),I));returnK(L(G,H),F);}functiont(G,F,aa,Z,k,H,I){G=K(G,K(K(n(F,aa,Z),k),I));returnK(L(G,H),F);}functione(G){varZ;varF=G.length;varx=F+8;vark=(x-(x%64))/64;varI=(k+1)*16;varaa=Array(I-1);vard=0;varH=0;while(H<F){Z=(H-(H%4))/4;d=(H%4)*8;aa[Z]=(aa[Z]|(G.charCodeAt(H)<<d));H++;}Z=(H-(H%4))/4;d=(H%4)*8;aa[Z]=aa[Z]|(128<<d);aa[I-2]=F<<3;aa[I-1]=F>>>29;returnaa;}functionB(x){vark="",F="",G,d;for(d=0;d<=3;d++){G=(x>>>(d*8))&255;F="0"+G.toString(16);k=k+F.substr(F.length-2,2);}returnk;}functionJ(k){k=k.replace(/rn/g,"n");vard="";for(varF=0;F<k.length;F++){varx=k.charCodeAt(F);if(x<128){d+=String.fromCharCode(x);}else{if((x>127)&&(x<2048)){d+=String.fromCharCode((x>>6)|192);d+=String.fromCharCode((x&63)|128);}else{d+=String.fromCharCode((x>>12)|224);d+=String.fromCharCode(((x>>6)&63)|128);d+=String.fromCharCode((x&63)|128);}}}returnd;}varC=Array();varP,h,E,v,g,Y,X,W,V;varS=7,Q=12,N=17,M=22;varA=5,z=9,y=14,w=20;varo=4,m=11,l=16,j=23;varU=6,T=10,R=15,O=21;s=J(s);C=e(s);Y=1732584193;X=4023233417;W=2562383102;V=271733878;for(P=0;P<C.length;P+=16){h=Y;E=X;v=W;g=V;Y=u(Y,X,W,V,C[P+0],S,3614090360);V=u(V,Y,X,W,C[P+1],Q,3905402710);W=u(W,V,Y,X,C[P+2],N,606105819);X=u(X,W,V,Y,C[P+3],M,3250441966);Y=u(Y,X,W,V,C[P+4],S,4118548399);V=u(V,Y,X,W,C[P+5],Q,1200080426);W=u(W,V,Y,X,C[P+6],N,2821735955);X=u(X,W,V,Y,C[P+7],M,4249261313);Y=u(Y,X,W,V,C[P+8],S,1770035416);V=u(V,Y,X,W,C[P+9],Q,2336552879);W=u(W,V,Y,X,C[P+10],N,4294925233);X=u(X,W,V,Y,C[P+11],M,2304563134);Y=u(Y,X,W,V,C[P+12],S,1804603682);V=u(V,Y,X,W,C[P+13],Q,4254626195);W=u(W,V,Y,X,C[P+14],N,2792965006);X=u(X,W,V,Y,C[P+15],M,1236535329);Y=f(Y,X,W,V,C[P+1],A,4129170786);V=f(V,Y,X,W,C[P+6],z,3225465664);W=f(W,V,Y,X,C[P+11],y,643717713);X=f(X,W,V,Y,C[P+0],w,3921069994);Y=f(Y,X,W,V,C[P+5],A,3593408605);V=f(V,Y,X,W,C[P+10],z,38016083);W=f(W,V,Y,X,C[P+15],y,3634488961);X=f(X,W,V,Y,C[P+4],w,3889429448);Y=f(Y,X,W,V,C[P+9],A,568446438);V=f(V,Y,X,W,C[P+14],z,3275163606);W=f(W,V,Y,X,C[P+3],y,4107603335);X=f(X,W,V,Y,C[P+8],w,1163531501);Y=f(Y,X,W,V,C[P+13],A,2850285829);V=f(V,Y,X,W,C[P+2],z,4243563512);W=f(W,V,Y,X,C[P+7],y,1735328473);X=f(X,W,V,Y,C[P+12],w,2368359562);Y=D(Y,X,W,V,C[P+5],o,4294588738);V=D(V,Y,X,W,C[P+8],m,2272392833);W=D(W,V,Y,X,C[P+11],l,1839030562);X=D(X,W,V,Y,C[P+14],j,4259657740);Y=D(Y,X,W,V,C[P+1],o,2763975236);V=D(V,Y,X,W,C[P+4],m,1272893353);W=D(W,V,Y,X,C[P+7],l,4139469664);X=D(X,W,V,Y,C[P+10],j,3200236656);Y=D(Y,X,W,V,C[P+13],o,681279174);V=D(V,Y,X,W,C[P+0],m,3936430074);W=D(W,V,Y,X,C[P+3],l,3572445317);X=D(X,W,V,Y,C[P+6],j,76029189);Y=D(Y,X,W,V,C[P+9],o,3654602809);V=D(V,Y,X,W,C[P+12],m,3873151461);W=D(W,V,Y,X,C[P+15],l,530742520);X=D(X,W,V,Y,C[P+2],j,3299628645);Y=t(Y,X,W,V,C[P+0],U,4096336452);V=t(V,Y,X,W,C[P+7],T,1126891415);W=t(W,V,Y,X,C[P+14],R,2878612391);X=t(X,W,V,Y,C[P+5],O,4237533241);Y=t(Y,X,W,V,C[P+12],U,1700485571);V=t(V,Y,X,W,C[P+3],T,2399980690);W=t(W,V,Y,X,C[P+10],R,4293915773);X=t(X,W,V,Y,C[P+1],O,2240044497);Y=t(Y,X,W,V,C[P+8],U,1873313359);V=t(V,Y,X,W,C[P+15],T,4264355552);W=t(W,V,Y,X,C[P+6],R,2734768916);X=t(X,W,V,Y,C[P+13],O,1309151649);Y=t(Y,X,W,V,C[P+4],U,4149444226);V=t(V,Y,X,W,C[P+11],T,3174756917);W=t(W,V,Y,X,C[P+2],R,718787259);X=t(X,W,V,Y,C[P+9],O,3951481745);Y=K(Y,h);X=K(X,E);W=K(W,v);V=K(V,g);}vari=B(Y)+B(X)+B(W)+B(V);returni.toLowerCase();};
scope.hash = md5(value.toLowerCase());
scope.size = attrs.size;
if(angular.isUndefined(scope.size)) {
scope.size = 60;// default to 60 pixels
}
});
}
};
});
2. Focus-Me
It is really just a small directive, but it’s awesome. In the example below the user clicks on a link, where he makes an input visible, which gets automatically focused. So he doesn’t need to clickinthe input field when it shows up.
/**
* Sets focus to this element if the value of focus-me is true.
* @example
* <a ng-click="addName=true">add name</a>
* <input ng-show="addName" type="text" ng-model="name" focus-me="{{addName}}" />
*/
app.directive('focusMe', ['$timeout',function($timeout) {
return{
scope: { trigger:'@focusMe'},
link:function(scope, element) {
scope.$watch('trigger',function(value) {
if(value ==="true") {
$timeout(function() {
element[0].focus();
});
}
});
}
};2. 關注我這其實是一個非常簡短的指令，但是非常棒。在下面的例子中，使用者點選了一個連結，顯示的輸入框需要能夠自動獲得焦點。這樣，使用者在頁面顯示時不必再手動點選文字域。
/**
* Sets focus to this element if the value of focus-me is true.
* @example
* <a ng-click="addName=true">add name</a>
* <input ng-show="addName" type="text" ng-model="name" focus-me="{{addName}}" />
*/
app.directive('focusMe', ['$timeout',function($timeout) {
return{
scope: { trigger:'@focusMe'},
link:function(scope, element) {
scope.$watch('trigger',function(value) {
if(value ==="true") {
$timeout(function() {
element[0].focus();
});
}
});
}
};
}]);3.Contenteditable元素模型繫結我們使用contenteditable而不是textarea元素的最主要原因在於使用前者可以在佈局和UI中沒有限制。我們在編輯器中使用這條指令可以實現將contenteditable元素的html和ng-model進行一個雙向繫結。目前，在contenteditable元素中並沒有支援ng-model。
/**
* Two-way data binding for contenteditable elements with ng-model.
* @example
*
*/
app.directive('contenteditable',function() {
return{
require:'?ngModel',
link:function(scope, element, attrs, ctrl) {
// Do nothing if this is not bound to a model
if(!ctrl) {return; }
// Checks for updates (input or pressing ENTER)
// view -> model
element.bind('input enterKey',function() {
varrerender =false;
varhtml = element.html();
if(attrs.noLineBreaks) {
html = html.replace(/<div>/g,'').replace(/<br>/g,'').replace(/<\/div>/g,'');
rerender =true;
}
scope.$apply(function() {
ctrl.$setViewValue(html);
if(rerender) {
ctrl.$render();
}
});
});
element.keyup(function(e){
if(e.keyCode === 13){
element.trigger('enterKey');
}
});
// model -> view
ctrl.$render =function() {
element.html(ctrl.$viewValue);
};
// load init value from DOM
ctrl.$render();
}
};
});結論：AngularJS指令可用於改善使用者體驗，我希望經過文中的介紹，你會感悟到AngularJS指令的有用之處。
對我而言，指令是AngularJS中最激動人心的特性。建立可重用的元件，並可以將其新增到純粹的HTML應用程式庫，這是多麼難以置信並且強大的功能。由於指令實用，並且大部分指令書寫難度不高，許多開發者早已對於目前受歡迎的庫開發了許多指令。舉例來說，AngularJS團隊已經為Bootstrap建立了一系列的指令（難道還有人不用它嗎？），被稱作UIBootstrap。
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